It's probably not a good idea to prank employees, especially if you don't know them well. It would be better to think of April Fools' Day more like a company event, allowing everyone to have fun while avoiding any hurt feelings. Though seeing as the holiday revolves around the act of pranking itself, it's safe to say that simple, silly and fun pranks like the classic whoopie cushion or computer monitor background swap are usually well-received. A good rule of thumb is anything that wouldn't interrupt the normal typical flow of work is best practice.