Usually they involve manipulation of some kind of object or law of nature...like turning a light on or off to see if the lighting level actually changes, checking a clock or reading text to see if it changes in odd ways, jumping in the air to see if your hangtime is unnaturally high, and stuff like that. There are lists of them in some threads - check out the Tutorials. Some folks recommend that you only do them when something odd is happening; others are of the school that if you do them often, you'll remember to do them in dreams.

I do very few RCs in real life...I had a phase of it but that phase has slipped, but I often do think to do them in dreams when something's weird...so I guess I primarily attain lucidity by recognizing dreamsigns, which is how I originally learned DILDing when reading LaBerge.

I sometimes use reality checks to confirm the dream-ness of things, but many of my most recent LDs have come from dreamsign recognition alone.