Fellow Weekend Warriors,
Here is a pressing issue which seems to be greatly understood by a lot of people. -especially beginners.
"OMG Trashed, I don't want [insert active pickup here] because they will frequently need batterizz."
Well... I have had quite a few guitars with active EMG's (81, 85, 60, etc.) and I have NEVER had one battery die in less than a year. The Gibson SG I have them in now have had them for five years (granted it doesn't get a ton of play).
The secret - don't leave your cord plugged into your jack. The jacks are switched (known as 'normally open') and the plug when plugged in completes the circuit.
The obvious disclaimers: just like you keep extra strings, DO keep extra 9V batteries around. If you get the guitar used, you don't know how long it has been in there, so I (just my preference) swap it, as opposed to wondering when it will die on me. Also, batteries are not all created equal. Tread carefully.
NOW for pedals...
MOST pedals have switched INPUT jacks, (like the switched jacks on active pickups) and will NOT drain batteries unplugged. If you leave them plugged in, (especially on a higher current pedal) you will have a dead battery fast.
Another argument is (regarding pedals), why the hell would you use batteries? They are expensive and unreliable as you don't know when they are going to die. The solution to that is a $25 Visual Sound (now True Tone) 1 spot will power your entire board, and will do just about everything you need. [For the record, an ISO powered block is much better, but you are looking over $100 easily for such unit].
"So Trashed, when do YOU use batteries"?
I use them as sparingly as possible. The ONLY time is if I am going to a small gig or open mic if I am running only two or three pedals, and you don't have to fuss about power and related issues. I test the battery before I put it in the pedal, and take it out RIGHT when I get home.