I agree with everything that BHC said. Thats exactly how you hunt a scrape.
However, in my neck of the woods, "it" seems to be starting already. No need to sit over scrapes anymore. Of course chances are they are going to be close to where you need to be anyway, so you can hunt near them. There is always a chance that they come to visit them. The bucks in my area are still cleaning out the breeding scrapes, and tearing up the overhanging branches, but they are really starting to troll and chase. I think they are cleaning out and checking the scrapes at night. Of course your area or BHC's area might not be into the chase phase yet.
If you go spotting at night, and you see big bucks chasing does, or if you witness it in the woods...try the following. Find doe bedding areas, and sit funnels/travel routes that lead into/out of them and you should see several bucks a day. They usually wait till mid morning when all the does are back in bed, then they come trolling through sniffing for a doe in estrous. If you're gonna call, try doe bleats (the can) and tending grunts. Some estrous scent works well too.
I didnt think this phase would start this early, it normally starts around the 7th, but I witnessed some BIG bucks "playing the rut game" yesterday. When the big boys start to chase, it usually means its getting closer to peak breeding. Which I think is actually the toughest time to hunt. Most bucks are tending does, and are impossible to call in, and almost impossible to find. They follow that doe EVERYWHERE she goes. When it gets to that point, try and call in does, they may have a big boy on their tail.
From chasing to breeding during the rut, HUNT the DOES! The bucks will be there![up][up]
Best of luck!