you can get a 1/64 sized rule at just about any hardware store. i believe i got mine at sears, or a local hobby store. it's important to ALWAYS write down ALL measurements before you start (ie, pickup height low and high with strings fretted at the 22nd fret, bridge height, tailpiece height, relief at 7th and 9th fret, height at 12th fret <unfretted>, and, what gauge strings are on it).
when i put 10-46 strings on my les pauls, they usually measure about 16-18/64ths on the sides of the bridge when im looking for 4-5/64ths at the 12th fret...and 20/64 when im looking for 6/64 at the 12th (which is usually my D drop C tuned axes, or sometimes lower with a 10-52 set on there).
you can pre set the bridge and tailpiece once you get the hang of setting up the individual axes and figure out what action works for you. also, even tuned to pitch, you SHOULD be able to raise (kinda hard) and lower your bridge with your fingers (your tune-o-matic bridge if you have one, can be adjusted by hand, i dont use pliers).
right on the side of the bridge you can set the rule next to it and measure.
when adjusting your truss nut, after you preset your bridge, an easy way to tell how much "play" is in each neck after you tune to pitch, give each string a preliminary stretch, tune back to pitch on all 6 strings, then fret the D or G string at the 22nd fret. you can use that as a straight edge (if you dont have one) now, keep that 22 fretted (a capo REALLY helps) with your guitar in the playing position and the truss wrench on the nut, be prepared to ONLY turn about 1/3 a whole turn, no more though, yet. if it's super tight, DONT tighten it more, it can snap off, and you're SOL. if it's loose as a goose, or is turning with minimum effort, well, count your turns...either way, count your turns. turning away from you should loosen the truss, thereby creating relief, turning towards the low strings should straighten the neck and reduce the relief (i forget what it's called). also, some necks love a really loose truss nut, some you would think wont straighten out until you have it pretty snugged up.
once you get a hint of relief at 7-9 frets (i usually like about 2-3/32 under my G string at the 9th fret, and your bridge should be pre-set correctly as stated above, on newer frets, you should be seeing around 4/64 unfretted at 12th fret on the low e, and 4-5/64 at the 12th fret on the high e.
some people tighten the tailpiece down all the way, i'm one of them, as, i like the increased sustain it seems that i get...and, i understring my LP's (through the tailpiece backwards, up and over the tailpiece, then over the bridge, up to the nut, thru the tuning peg).
there are several different ways to string and wind on the tuning peg, i go through, then under, then over...hard to explain, but, it looks like this:
https://www.youtube.com/watch?v=xh77SRuLPsE
good luck, stretch your strings, and be prepared to make adjustments on the fly.
there are a lot of good tips in this thread. one of my secrets to long string life is graph tech saddle string savers and nut sauce, or, a pencil ran back and forth along the nut grooves.
i like my screws on my tuning posts winders to be tight....it helps keep that notorious g string les paul syndrome under control.
something to keep in mind too, if you live in a climate like pittsburgh that is pretty humid and has pretty drastic seasonal changes like we do here, you'll probably notice your guitar's action is going to "float" a bit throught the year....this is normal.
when i do my seasonal set up (usually december or january and june/july) i remove all strings after i measure, and let the neck settle without strings on it. you can do this by hanging it on a guitar stand, or sitting it in a stable chair (leaning face against the chair, headstock pointing straight up in the air....but no pressure or "lean" on the neck).
i call this, letting my neck breath. it's just something i like to do. some people would tell you to NEVER leave a neck naked like that, but, like i said, to each his/her own.
good luck with it. learning to setup and take care of your axes is a well rewarding labor of love, and you'll thank yourself for learning how to do it. if you get mad, or get stuck, or frustrated, take a break...come back to it a bit later.
good luck
G
ps, wow, sorry for that big ass bridge pic..but, right along side that, straight up and down is where you would measure.
