These go from lowest to highest in cost, time, and performance boost
1. Get a calibration disc like AVIA and use it to fine tune your basic settings 9cists about $25-$30, and can make a noticable difference)
2. Do some internet research/join a home theater forum, leanr how to get into the service menu and use that and AVIA to do more modifications (allows you to fix any color pushes or pulls you may have, adjust geometry, overscan, pixel cropping, blanking, and a few other things. Also allows you to set the controls in the service menu so that all the basic picture menu settings are correct at midway).
3. Shell out aa couple hundred dollars to have a good calibrator spend a day with your TV and get it as good as it can be.
I've done numbers 1 and 2 myself.
What kind of TV do you have?
I've got a 20 inch Sony Wega, and it looks pretty darn good...I've done quite a few tweaks in the service menu.