I've just written up my first brew log & asked myself the same question. I agree with brewchez - it depends what you want.
I started with brewchez's log, but as I'm going to be using simple extract-based recipes while I figure this out, it was too complex. I started with Palmer's example in 1.2.3 Record Keeping and as I started filling it out, found I wanted to record a lot more information.
Since I'm new at this, my goal is to record as much data as possible, so I can best learn what factors influence the result & how. Here's what I have.
Type/Name:
Volume:
Date (fermentation):
Date (bottling):
Date (taste):
Yeast: (form, type, pitched?)
Temperature notes: (primary range, secondary range)
Malts: (qty, type for each)
Original Gravity: x.xxx (measured/calculated)
Final Gravity:
ABV:
Hops:
#. qty, time, type, %AA
IBU:
Sugars: (added during primary, priming)
Yield & vessel: (glass/plastic bottles, kegged)
Notes:
Picture:
My personal favourite thing here is the picture. I look forward to having a photo of every beer I've ever brewed. Make sure you use a white background (I use a dinner plate) so the colour is accurate.
I also use Evernote to store my notes. It's searchable, like Google Calendar and stores pictures too. You could just as easily use OneNote, Google Calendar, GMail, DropBox etc.
Good luck!