I live on a 185-acre farm, in the middle of a few thousand acres, mostly all wooded, and can hunt all of it. In Arkansas we have two squirrel seasons -- from mid-September to the end of February, and from mid-May to mid-June. That's about 6 1/2 months of squirrel hunting, more or less. As you can imagine, I get in a lot of it.
1. Scout the habitat. Squirrels like big, mature hardwoods. Hickory and oak are good squirrel territory (although they eat lots of other stuff, too.)
2. Go out early. I often go out before first light, just to see the woods come alive.
3. Be patient. I have a folding stool with a shoulder strap. I sling that and go into the woods and set it up, so I can rest my back against a tree and just wait. In a good spot you can get several squirrels just sitting still. When you shoot one, mentally mark where he fell and sit still -- they'll be back out in a few minutes.
4. I use a .22 (a Model 82 Kimber with a 4X Burris mini-scope.) I practice a lot with that rifle and take advantage of a "lean" against a tree whenever I can.
5. When walking up squirrels, go slow. Take a step, look and listen.
6. Learn to shoot fast -- you'll often see a squirrel feeding on the ground. For fun, you can try to stalk him -- but for meat, jshoot as soon as you see him.