Well you can always put some sun screen on and lay outside for a little bit to at least fade the tan lines. If you tan easily, this won't take long. But if you don't then it's not a vey good idea to sit and bake in the sun, so you could get some spray tan.
A trick I leanred from a magazine that I have used before is to get some bronzer or foundation and use it on the tan lines.
self tanner its a instant tan but make sure what ever kind you get you rub it in really well and try going out side aswell and staying in the sun but make sure you protect your skin! also you could just body scrubs on your legs, that gets rid of the dead skin as gross as it sounds it gets rid of your tan