How to cool down a room ???

out of all the rooms in my house mines the warmest my mom thinks its because i have a computer in my room it heats it up plus i got a big bed in kind of a smaller room is their anyways i can cool down my room a bit maybe moving things around maybe adding some plants i herd it can keep the room fresh feeling and would it be a bad idea to put my computer in my closet i dont have doors on it just pull back curtains ? could it be fire hazardous ? .....sorry ignore my spelling people :)