When I'm home or at one of my family members' house, I'll leave the WiFi on, but if I'm at work or out and about on the town, I usually shut it off unless I need it, no sense leaving it on if it's not connected to anythino, all it does is keep refreshing and looking for a remembered connection
My apartment has pretty crappy reception too, but luckily, my Droid actually has good service in every room (usually at least 2-3 bars), whereas my last phone (i760) would have 1-2 bars and I couldn't use it in the kitchen at all.
I also just noticed that I'm getting better battery life switching kernels. I was using the Low-voltage 1GHz p3droid kernel but I was losing about 10% of my charge per hour under moderate usage (I have eBuddy going, Bloo checking Facebook every 2 minutes, plus my normal checking texts and facebook notifications as they come in). When I got down to 50% I switched to the 1GHz bekit kernel and in 3.5 hours I just now went down 20%, so I just hit 30%, and that's after removing my phone from the car charger at 9:45am (It's now 7pm). It seems like it's given me about a 40% increase in battery life (It's about 5.7%/hour now instead of about 10%). These numbers are rough, but accurate enough. I didn't log exact times, and my Droid only reports battery life in 10% increments, but I've been playing with it enough to be fairly confident with these figures.
I noticed that I had to bump down the overclocking when I have it plugged in my car too, if I left it at 1GHz when using Navigation it still sucked down about 20% of my charge on a 1.5 hour drive, and using Slacker on my way into work used about 10% of my charge for a 45 minute drive... But bumping it down to 700MHz when plugged in with SetCPU let me start off my day with an almost 100% charge