I have changed several outlets in my home,now when I plug in different items they overload my breaker.My outlets have six wires that I'm not sure I have correct. I saw something about a pigtail in a book but I don't rember where. Can anyone help?

At least 2 wires will be at receptacle, Usually a white wire(goes on receptacle white/silver screw) and the hot goes to the other side on the dark screw.
If you have more than one white or hot, then you will connect a 6 inch piece of wire
(Pigtail) to connect to receptacle.

If you have six wires per outlet you probably have two grounds (bare copper), two neutrals (white) and two hots (black). Connect both grounds to the green screw on the receptacle, both whites to the silver screws, and both hots to the gold screws.