AARONS - I know that we are responsible for our actions and Satan has no power except as we permit it. Does that include bad thoughts? When we have bad thoughts is it satan putting them in our minds? If so how can we block bad thoughts from popping in our minds?

JOEL - Satan has been called the "father of all lies" because he is the source of all evil. As you say he can not force us to do evil but he will tempt us with situations and thoughts which can cause us to fall if we act on those thoughts or continue to dwell on them. The scriptures tell us:

"there is none else save God that knowest thy thoughts and the intents of thy heart." (D&C 6:16)

Even though Satan can't know the true thoughts of our hearts he can attempt to place some of his own into our minds if we let him. Joseph Fielding Smith said:

"We should be on guard always to resist Satan's advances. He will appear to us in a person of a friend or a relative in whom we have confidence. He has power to place thoughts in our minds and to whisper to us in unspoken impressions to entice us to satisfy our appetites or desires and in various other ways he plays upon our weaknesses and desires." (Answers to Gospel Questions, 3:81)

Considering the fact that we are plagued by the "natural man" aspect from living this mortal life(1 Cor. 2: 14, Mosiah 3: 19), it is virtually impossible to block out all bad thoughts from our minds. But there are things we can do to keep most of them out and make all of them leave. The D&C tells us:

"let virtue garnish thy thoughts unceasingly; then shall thy confidence wax strong in the presence of God; and the doctrine of the priesthood shall distil upon thy soul as the dews from heaven." (D&C 121:45)

Sounds good but how do we let virtue garnish our thoughts unceasingly? First of all we need to start out with the right attitude in terms of our relationship to God. In the D&C we read:

"And if your eye be single to my glory, your whole bodies shall be filled with light, and there shall be no darkness in you; and that body which is filled with light comprehendeth all things." (D&C 88:67)

Light and darkness cannot occupy the same space. Light will always dispell darkness. We just need to remember to turn the light on when evil thoughts start to enter our minds.
Dedicating our lives to the will of God and seeking to increase His glory will fill us with that light which will help put our minds and spirits in the proper frame of mind to help keep out the bad thoughts.
We must do all we can to keep ourselves out of situations, places, and thought patterns that could result in the generation of bad or impure thoughts. We need to keep ourselves involved in good works and activities that helps maintain the presence of the Holy Ghost in our lives.
Our minds can only think of one thing at a time; if we keep ourselves thinking about good positive things we can crowd out the bad. Have some scriptures memorized that you can repeat in your mind; say a prayer; recite a good poem; or perform some act of service for someone.
Elder Boyd K. Packer offers the following advise:

"Choose . . . a favorite hymn . . . one that makes you feel something akin to inspiration. Go over it in your mind carefully. Memorize it. . . . Now, use this hymn as the place for your thoughts to go. . . . Whenever you find these shady actors [shady thoughts] have slipped from the sidelines of your thinking onto the stage of your mind, put on this record, as it were. As the music begins and as the words form in your thoughts, the unworthy ones will slip shamefully away. It will change the whole mood on the stage of your mind. Because it is uplifting and clean, the baser thoughts will disappear. For, while virtue, by choice, will not associate with filth, evil cannot tolerate the presence of light." (Conference report 1986 Oct:100)