couple more things while reading this thread again:
only order a bike from an actual BMX store (i.e. http://danscomp.com
) dont get specialized, gt, mongoose, and all that other crap your local "outdoor and cycling" store carries. chances are they wont have the newer companies that make much better bikes.
look for a frame that is at least a 20.5" toptube. im 6'2" and ride a 21" and would never go any shorter. given that you are buying a complete, bikes that are 21" are generally a lot more expensive. also you want a bike that has as much full chromoly as possible. you probly wont ever notice a difference but full chromoly is more durable and is a little lighter so just shop accordingly. for $400 or less you can still get a kick ass bike with a 20.5" tt and at least three main frame chromoly-which is awesome. dont worry too much about those specs
you dont need triple wall or whatever rims. i run double wall rims which are fine. unless you are from 1995 and want a bike that weighs 40 pounds you dont need 48 hole rims and triple wall rims. complete bikes anyways mostly come with 36 hole rims. just invest $5 in a spoke wrench and make it a routine to tighten your spokes every week or two and you will be fine. which you should be doing regardless of your wheels.
brakes. dont go brakeless because it's cool and lightweight. buy a complete w/ brakes and you can always take them off later. some new completes are brakelss w/o mounts which is a bad idea as a beginner. learn tricks w/ brakes now and then decide what you want.
axles. i personally run 14mm front and rear just because i dont want to buy a new front hub. 14mm is a necessity in the rear but unnecessary in the front unless you are 200+ pounds and grind the shit out of things. get a 3/8 front and you will bne fine. they heat treat axles so the axles will provide ample strength.
just get the fbm. it is a great bike from a real bmx company.
hope that helped and pm me with any more questions.