Squirrel hunting is a lot of fun and just like any other critter, prepared right can be really good eating.
Here a couple things I learned from a buddy of mine from Arkansas who is a real Squirrel hunting aficionado.
1. Most folks simply throw their harvested squirrels on the ground. They tend to curl up in a ball and when they stiffen up in the ball and are harder to clean. Avoid this by taking a small stick and sharpen 1 side with your knife. Stab it between the tendon and bone just above the Ankle. Allow the squirrel to hang straight which significantly helps for cleaning later. Just add to the stick as you kill more.
2. There is a art to cleaning a squirrel. Here is a good link on how to.
http://s428.photobucket.com/albums/qq5/greybeard49/?action=view¤t=SquirrelSkinning.flv
3. Squirrels feeding on pine cones can have a piney/tar taste
4. Avoid pan or deep frying older squirrel as the meat can be tough which I think has given squirrel meat a bad name for a lot of folks. In the case of older squirrel I pan fry then put in a mushroom gravy in the oven for an hour or so. Also brining (water, salt, sugar)your squirrel prior to cooking also gives you a very juicy and flavorful meal.
5. How do you tell if a squirrel is older? Simply take one of its legs and bend it. If it is somewhat flexible, it's young. If it feels like it's gonna snap before it really gives, it's older.
I suppose you can follow this for rabbit as well. I have always heard never eat rabbit until after the first freeze due to the aforementioned disease rabbits carry.