That's an excellent question. The main thing to remember is that elves are incredibly quick and agile, so you'll need to be just as quick and agile as they are. First, you'll need to lure the elf out of its hiding spot, so you'll need to use a clever trick. A classic strategy is to use food as bait - elves are very fond of candy and cookies. So if you leave out a plate of cookies, there's a good chance the elf will sneak out to grab a few.