A Ouija is supposed to spell out messages from the dead. Playing about with one is highly dangerous. It can influence the Mind to such an extent that it can lead to nervous breakdown. Leave these boards well alone!
A pentagram will not harm you in any way. It will protect you from "negative" energy. It is a very old, very very old,magic symbol and is connected to the planet Venus. When the pentagram is enclosed in a circle it is called a pentacle. It is often worn as a pendant/necklace. I have a silver one on a silver chain, I wear it always.