well, there is a few different ways to tackle this depending on the severity, and what panels it is that are affected. Meguiars PlastX is a fairly competent product, just be sure to work it fully until the abrasive breaks down properly otherwise you will leave micro-marring behind which will need re-polished out.
If you have access to a DA or rotary, it can make the process much more efficient and a bit quicker.
I tend to find that the finish left after PlastX is usually not amazing (It does a bang up job of taking the scratches out, granted), so I tend to go over the top with a much finer diminishing polish, such as Menzerna Final Finish, or 3M Ultrafina. It depends just how shiny you want it afterwards (and of course, if you do go to this level, you will probably need to do the rest of the bike with a finishing polish as well, or else one panel will stand out more).
Dotn forget once you have used plastX etc you will have stripped any wax/protection you have laid down, and so you may want to consider firing something over the top to give some UV protection and make the bike easier to clean
Oh, and dont forget to take plenty of pics!