All I did was let the battery drain and completely recharge a few times after I got the phone.
Pretty much everything that wants to use location and notifications is enabled to do so. Siri is enabled, but I never use it. Bluetooth and WiFi are enabled, though I only have the networks at my apartment, my sister's house, and my mom's house programmed in, so at school and work I'm on 3G with an excellent signal at school and a weak to moderate signal at work. I tend to keep both the ringer and media volume set at 50%.
I play casual games on and off throughout the day (a few rounds of Ninjump and Jetpack Joyride, and taking my turns in Hanging/Words with Friends). Sometimes I'll fire up Infinity Blade for a while, but it drains the battery more quickly, of course. I play Pandora and answer calls through Bluetooth in my car when I'm driving. Throughout the day I'm firing off messages in Messages and/or Facebook Messenger to my girlfriend, family, and sometimes other friends. I don't talk on the phone much. I also sometimes check my bank and credit card accounts through the respective institutions' mobile apps. The camera gets occasional use as well, as does Safari.
Though I haven't kept good logs and run the numbers or anything, my normal pattern seems to result in a charge lasting about 20-24 hours with 6-7 hours of usage in that time. Just going by the times I've seen, on standby the phone would probably last a few days on a charge, which isn't bad for a modern smartphone. I don't know how this compares to previous iPhones. It's comparable to my original Droid, and a good deal better than the Rezound I briefly tried before making the switch.
Really, depending on what those 5 hours of usage entail, a 15-hour charge may not be too bad. Apparently previous iPhones had amazing battery life, but there's a lot of hardware packed into the 4S. While some of users' issues may be the result of software glitches or whatever, at least part of the problem is likely just an indication that battery technology isn't completely keeping up with mobile hardware technology.
Good luck to you, though, in finding a way to make your battery life live up to your expectations.