BigDaddysMom - It's quite easy - just get a big pan of water that's at 99-100F, let it sit till the water stops swirling, then carefully lower an egg into it, the same way up as it's been sitting in lockdown. Give it half a minute to settle, it should sit almost submerged but with a small bit of the fat end out of the water, then watch for ripples. First time I did it was with all dead eggs, but each time I shifted my weight from foot to foot, the pan of water on the table would ripple a bit. I wasn't sure if I was seeing the eggs wobble or not. Then when I did it with a live egg, wow, the difference was amazing. It was jigging about all over the place. I don't think doing this puts the chick at risk as long as the water is at the right temp and you don't float the egg for longer than a minute or so. A good idea before you do that is to just hold each egg up close to your ear and listen. Sometimes you can hear tapping noises, and you won't even need to do the float test. And check each egg carefully for pips before you float them!
Some people would still recommend that you just sit tight and wait a bit longer, and don't disturb the remaining eggs. I think that's probably very good advice! I only started floating my remaining eggs after a few hatches with my own birds' eggs, all the same breed, where I observed that everyone that was going to hatch did so all together and I never had any latecomers. If I was incubating a different breed that I didn't have experience of, I'd probably sit on my hands a bit longer and just see what happened...