The thinner trim pieces on the door just below the window(s) is held on by clips taht are riveted to the body. In order to remove them you must gently push the trim up enough to then be able to pry the top edge off of the clips, after which you can let the trim descend enough to release it fromt he bottom part of the clip. Replacement clipas are available if yours are rusted. I used pop rivets to reinstall the new clips.
Windshield trim: I presume you are removing the trim in order to replace the seal, in which case, I would carefully cut through the seal along the trim pieces to release them. As George says, release the sides, and then carefully and concurrently, slide the top and bottom out from the center. I've never removed the trim in order to just replace the trim -