What to do when she's grinding me?

Okay... so Ik this is kinda dumb... but I'm kinda clueless still when it comes to girls grinding on me... and I have a girlfriend now that I've been dating awhile, and I know she's way into me... and she's talked about it with other ppl before that she'll try to help me out. But I just need some tips to not look like a complete dork and maybe impress her a little?? It'd be much appreciated