Ouija boards are simply tools, they are not good or evil. When the user hasn't a clue what they're doing is when bad things happen. I have dealt with Ouija Boards for about 7 years now and there has only been two occasions when we ran into trouble, but both times was a result of the people using it. The first was a spirit who hated my one friend and made it a point to bring her problems. We wound up cleansing the house and she had to wear a protection amulet until she moved away because the spirit was still hanging around the property [and she owned a lot of land] the other time a different friend yelled at a spirit. She just had to apologize but still, not fun.
Before you use the board, cleanse and charge it, especially if you bought it. When you are going to use the board, cleanse the area and the people using the board before and after to get any negative energy or lingering spirits away. If you feel safer, cast a protection spell or wear a protection charm. After cleanse be sure you cast a circle. Ouija Boards are spiritual magnets, any passing spirit is attracted to it, the circle will act as a filter stopping negative beings from communicating. However, they will be outside the circle waiting, hence cleansing a second time. Finally, store the board in a safe area where it won't get damaged.
Couple things to remember, one, people lie. Someone you are working with could move the planchette to play a prank, it is better to have the people blindfolded and have someone [or a camera] record the results. Two, spirits lie. Some are tricksters, some are lonely, whatever reason, spirits can tell tales so don't believe everything they say.