If you just google it there are tons of threads about this. However, it all depends on how much money you want to spend and how low you want to go. If you want to just get the basics, you can get by with springs and an adjustable panhard bar. If you want to go all out, you can get that along with new shocks and struts, camber plates, control arms and sway bars. I just lowered my 07 GT with Steeda Sports and just added a panhard bar and my camber was still good. But it has been about 4,000 miles and my shocks and struts are starting to go since it is a lot harder on them. I would recommend doing it right the first time, get your springs, panhard and Koni shocks and struts. You will be glad you did trust me!
2007 Mustang GT 4.6L V-8, 5SPD, FRPP 4.10, JLT CAI and 93 BAMA Race Tune, JBA Longtube Headers and O/R H Pipe, Pypes Pipe Bomb Axle-Backs, Koni STR-T, GT500 Strut Mounts, SR Springs, BMR Panhard Bar and Support Brace, BBR LCA'S, SR Strut Bar, MGW Shifter, GT500 Wing, Roush Louvers, CDC Chin Spoiler, Blacked out Windows and Lights, 6000K HIDS, 19X8.5 and 19X10 Black Bullitt Wheels, Pioneer