Well, the nose one always works for me, but that's just me. There's actually a tutorial you could look at that has a lot of ideas, but I'll throw out a suggestion or two.

One time I thought I might be dreaming, so when I looked down a hallway the first time, I saw a group of people, but when I looked away and looked back they were gone. Looking twice at something to look for changes can be very effective. Things are always changing in my dreams.

If you're already fairly sure that you're dreaming, you could try jumping up into the air and try to fly. If you manage to, or even if you stay in the air longer than normal, you could still use that to realize or confirm that you're dreaming.