Nah, that's in advanced troubleshooting. Along with jumping up and down and screaming
My favourite is re-soldering with an arc welder. 400 amps or thereabouts makes for impressive results.
"Fixes" things every time - just remember not to burn your home down while trying this...
I've got a bit of a temper so I tend to bang things or throw them against the wall. None of that advance troubleshooting of mine has ever worked of course. LOL But it still happens every now and then. 
Arc welding? I don't think I'm even ready for regular soldering yet. 
I was just going to use vaseline but I thought I'd use what the flashlight experts recommend. 
Maybe we could add a section about "First steps with your new light", as most of my problems have come from loosely tightened switch and light modules. This guide will be really good, thanks to all for what you can add to it.
That's a good idea.
Probably split this up into something like:
First steps
Preventative maintenance
Basic Troubleshooting
Trickier troubleshooting
Electrical and optical measurements
Soldering
Replacing components
Take a while to illustrate all of those though. Will try to get pics of sorting out the Aurora light above in the near future.
Yes that looks good, Don. Let me see if I can play around with some formatting options here...
It is rather messy - I was fiddling with the light and typing as I went along. Pretty it isn't.
Not at all, no worries, we're just outlining at this point.
Whether it's a $10.00 Trustfire or a $250.00 Surefire, almost any flashlight can arrive with problems out-of-the-box, or it can develop problems later on in its lifespan. However, most of these problems are easy to resolve with minimal tools, even for somebody who is not particularly handy.
Something like that? Suggestions are welcome.
Looks good to me.
It might get to be rather long though - maybe some of it as separate posts?
Also perhaps in big red letters at the top, the very important motto; "if it ain't broke, don't fix it!"
Or the troublesome tradesman's variant; "If it ain't broke, fix it till it is..."
If it gets too long an unwieldy I can look into splitting it up or we can put an index at the top. We'll figure something out.
First Steps with a New Light
So, your new light has arrived. As it happens, one arrived for me today. So we'll use it as an example. It is one of these a flood to throw light. Having got it out of the packaging, it is not a dreadfully good idea to throw the packaging away. You may need it to return the light, of there may be things lurking it it. In this case I found a nylon holster lurking in the bottom of the box. So having found all the parts, we can put the packaging aside.
A visual inspection is always a good idea. So here it is.
Looks OK.
Does it rattle?
What I usually do next is give it a gentle shake. Are there any rattles or bad sounds? If there are, put a battery in it and try again. They shouldn't rattle - if they do, something is loose that needs to be tightened up. The first places to look are the switch retaining ring and the pill. If they are loose, you are going to get flickering or worse. However, this light, being a zooming light has to be checked with the head at the various settings. There is a faint rattle at the farthest extension (Tightest spot). The whole head will rock slightly at this setting, probably because there isn't enough body tube to keep it in line. There was a small amount of movement from the aspheric optic. Don't touch it with your fingers, if it is coated glass you will damage the coating, if it plastic you will scratch it. Use a lint-free cloth or anything you'd clean spectacles with. Tightening up the bezel ring fixed that. You can see the gap for the bezel ring quite clearly in this picture, far more clearly than I could actually see it. There are no other rattles so we'll set aside the head issue for the moment.
Inspect the threads
Just a visual inspection just now. Tailcap first as it is easiest.
This photo doesn't show it but they are covered in some grey crud - which may, or may not be a lubricant. Judging by the squeaks, if it is a lubricant it isn't doing its job. So I'll clean the tailcap threads. I find the best way to do this is with some toilet paper which I push into the threads with a fingernail and then twist the tailcap around to use my fingernail and paper to follow the threads and clean them out. A couple of pictures to explain.
I have my thumbnail engaged in the threads and am using it to push the tissue into the threads.
Fold the paper back so we can see the threads.
Here's what came off.
We'll set the tailcap aside for the moment. Obviously there is no point at all in only cleaning half of the pair of threads, the body tube is going to need cleaning too. As it happens there is a huge (maybe 1mm long) lump of crud stuck to the black stuff so it needs a good clean too.
Before
You can see the lump of crud at about 5 o'clock. Same technique to clean the body threads. You can, of course use a cocktail stick, toothpick, scriber or whatever, I just tend to use a thumbnail because it is hard to lose.
Here's what came out of the body tube.
Yuk!
So we now have nice clean threads. And boy do they sound like dry threads. Not nice. So we'll put a little silicone grease on the threads and O rings. Then we'll wipe most of it off. I usually apply a blob to the threads of the tailcap and screw in in and out of the body tube. The O ring should get lightly coated too. Lubrication is a matter of personal preference - many people prefer a lighter lubricant - maybe even most, but I prefer a heavier one even though I end up wiping most of it off again. I've been using the same tube of silicone grease for more than ten years and the stuff is dirt cheap. If you perfer a runnier lubricant, feel free. The trick is Don't Use Too Much. You'll just have to clean off the threads again. Remember that lubricants are an electrical insulator and you are depending on those threads to transmit current. Don't fill the gap with so much lube that it won't work.
So I apply a small quantity of lube
Then I screw the tailcap in and out and make sure the O ring gets well greased. Then I remove the tailcap and clean the threads just as I did at first. There will be plenty grease in the threads of the body tube now and I can give the O ring a little more if I feel it needs it. It does so another very small amount gets applied to the O ring - an amount about the size of a match head is too much. I wipe this round the O ring then go and wash my hands - I loathe the feel of silicone grease on my hands.
I'm now in two minds about the movable head. In this case it's meant to move and it is friction that keeps it in place. However, the feel is horrible so do I lube it or not. Nah, that can wait, after all it's not yet been dark since I got my new precision instrument toy. We'll see what it's like in a day or two.
This one's head is not removable so I don't have to repeat what I did with the tailcap.
Of course what I actually did was ripped open the package, pulled out an 18650 and made sure it worked. The I played with it till it was time to go to work. Now that I'm home from work I've done the preliminary inspection.
Great Don! I can't add anything to that. Very clear. I can clean up some of the other posts in this thread later on.
I've picked a list of useful items (mostly from DX), none of which cost all that much. Not sure where this belongs, but here seems as good a place as any.
Some sheets of paper 11x17 or A3 for laying stuff on where you won't lose it. It is much easier to find small parts on a sheet of white paper. Also makes sure your work area is clean.
Some copper wire. I use solid core Cat5 ethernet cable. It is cheap - for under $50 you get about 1000 feet of the stuff which gives you 8000 feet of solid copper wire. A foot or so of the stuff ought to be free.
Some copper braid - usually sold as desoldering braid. http://www.dealextreme.com/details.dx/sku.9159
Some small screwdrivers. These DX ones are cheap enough to use as devices for moving switch retaining rings around. http://www.dealextreme.com/details.dx/sku.6060
A set of picks and probes for fiddling with stuff. http://www.dealextreme.com/details.dx/sku.34527
A spudger or two can be incredibly useful for prying stuff apart. http://www.dealextreme.com/details.dx/sku.19279
Plastic spudgers are handy too, they won't damage anything themself but have to be treated as consumables. Any mobile phone opening kit will contain some. http://www.dealextreme.com/details.dx/sku.3006
A pair of fine pointed tweezers. http://www.dealextreme.com/details.dx/sku.19869
A pair of straight tweezers. Matter of choice which sort you prefer. http://www.dealextreme.com/details.dx/sku.19872
A set of fine nosed pliers. Something along these lines. http://www.dealextreme.com/details.dx/sku.7024 I tend to use a Gerber multitool
An air blower for blowing out dust. http://www.dealextreme.com/details.dx/sku.12969
A lens cleaning cloth. Any optician will sell you one. My personal preference is the "Calotherm" brand but any lint-free cloth will do. This micro fibre one might be good but isn't all that cheap. http://www.dealextreme.com/details.dx/sku.34097
Some fine (800 grit or finer - I use 1200 grit) wet and dry sandpaper or a diamond file. The diamond file need only be about 1 x 3" (25x75mm) and should be as fine a grit as possible. They are very cheap nowadays.
A flathead screwdriver of about 6" (15cm) length. Mostly to be used as a pry bar.
Optional: This watch repair kit contains all sorts of useful bits and bobs but may not be strong enough for playing with bezel rings and the like. http://www.dealextreme.com/details.dx/sku.15374
Optional: But very useful for all sorts of things. A set of circlip pliers. Useful for bezel rings and switch retaining rings. Don't buy expensive ones, these tend to become consumables. http://www.dealextreme.com/details.dx/sku.8484
Optional: A cheap watch case cracker - I can't think how to describe it so I'll take a picture of it later
Optional: A set of cheap haemostats (artery clamps, locking tweezers) in various lengths and tip shapes. I use mine a lot.
There are hundreds of other items I could add such as strap wrenches, vices, hammers, drills and so on and you won't even need everything on this list and there are very likely things on this list you'll never use or can get away with a field expedient. Because I'm 50 this year and getting long sighted I always end up using a wide range of magnifiers but if your eyesight is better than mine you won't need those - I didn't till I was 45.
It would be nice if you did not include all the other posts......would make a new comer have to read all the info before he found all the nice tips.
We'll need to get them written first though. 
You bet, I'll clean it all up or consolidate it into a single clean post once we get the content finalized. Thanks for everyone's hard work!
I have another non-functioning Aurora SH0030 (5 mode this time) to sort out. Pics this time once the sun comes back up. Still have a lot of work to prepare for Sunday and Monday so will try to fit in the photography.
Since it is a nice day I went out and cut the grass for the first time this year (We had snow 2 weeks ago). Then dug out the camera and illustrated the basic repair article above. #13
Enjoy!