Ribbon edge connectors are usually just pushed into the socket. Sometimes they have harder plastic tabs which help pushing them back in later. I usually try to pull evenly from both sides at once, or sometimes use needlenose pliars to get a light (but firm) grip of the entire ribbon and pull it straight away. Molex connectors (the white ones) are just like any plug, they usually don't have locking tabs for smaller connectors, but it's always a good idea to look carefully. a small screwdriver can be used to pry them out, but I usually just risk the danger and pull on the wires...