Selecting parts is a fun part, especially if you want to be pretty systematic about it.
A little brushing up. This a reasonable reference for some of the basics, primarily for duty factor, and ripple vs frequency and inductance.
http://rohmfs.rohm.com/en/products/databook/applinote/ic/power/switching_regulator/inductor_calculation_appli-e.pdf
But I'll cliffs notes. (I don't like how casually it treats many of the linear approximations and averages, but ok)
It derives a detailed form of the duty factor including voltages losses in switches and diodes, but then I like the Ti approach of just calling it
V0/(eff*Vin).
The ripple current vs frequency and inductance is useful (and maybe helpful for choosing the inductor size and switching frequency) but also it's included in equation 10 here, a better document anyway:
http://www.ti.com/lit/an/slva390/slva390.pdf
Useful to go through all that, but equation 11 summarizes it. But better to look at 7 and 8 instead. 7 is the mosfet loss and 8 is the freewheel diode loss except they use a mosfet there too. For the diode I guess you have to look at the loss as Vf*I instead of I^2R, simple enough change. So that's losses for both of those components.
Oh and equation 4 gives the inductor loss, which is almost stupidly just I_out^2*R_L. So that's easy to figure too.
However you get to equation 12 and they say blah "+ other losses"
Oops, some nastiness there to figure out, especially switching losses, that looks fun:
http://www.allaboutcircuits.com/technical-articles/switching-losses-effects-on-semiconductors/
Oh, why was Ti using a Mosfet instead of a diode?:
So there's that too, but I don't think it's compatible with your IC.
Then there is discontinuous current mode to worry about at very low power probably.
But that's all just introductory for basic bucks. This 3409 looks pretty fancy (aside from using a diode I guess), with variable frequency, off time control etc. I'm just starting to look at its actual docs. I prefer their math actually. They don't make the approximations so casually, but then they don't start with -LdI/dt either, so that's too bad, unless you only want answers.
Anyway, the obvious things are obvious, keep Rdson low for the switch, diode Vf low, inductance high, frequency high (but not too high, see that link about switching losses, last figure), capacitor ESR matters significantly less, and here already are a few simple guidelines to put numbers on some of it. I think it's really not so bad.