Turn your resolution down to 640-480 and turn the effects on your games all the way down. That should give you optimal frame rates! Or you could just put the thing together, crank it all to the max and revel in the awesome spectical that is your new computer!
Seriously, without overclocking, you can't "tweek" much out of your computer, and you shouldn't need to, it's a great system. Keep your drivers up to date and keep programs from running is the background, that's my best advise. The advantages tweeking little things might give you aren't going to be noticable. What's one more FPS? By the time the computer's having problems with current games, the extra 1 FPS from a tweek isn't going to help you anyway. Just make sure you set everything correctly in your bios and install all the drivers and whatnot and don't worry about it.