Great thread topic! I'm glad to see there's others who have approached lucid dreaming from a pragmatic angle, and not a "spiritual" one.
I consider a true "lucid" dream to be the type where you realize you're dreaming, and then suddenly the dream becomes what I call "hyper-real". Details, colours, even a sense of "space" around you suddenly jumps into sharp relief. I've found smells, taste, sounds etc. all become quite intense. Also, you can pretty much do what ever you want, from flying to turning invisible (must be a latent voyeur or something, but that's a favourite of mine) to just standing there going "wow, I'm in a dream right now, and I can do whatever I want!".
I can only induce these states with practice and routine. Years ago I was getting quite good at it, but I haven't had a truly lucid dream for going on 9 or 10 years now.
The way that I did it was by teaching myself a routine of doing "reality checks" during the day. This generally consisted of looking at street signs, or anything printed, reading it, then looking away and turning back to read it again. If the words remained the same, then I wasn't dreaming. However, a unique aspect of dreams, is that printed words are never static, so the second reading is what would trigger my lucidity. As soon as I saw that the street sign was completely different the second time I looked at it -- Bam! my dream was lucid. The trick is that if this is a routine behaviour in your waking life, then it will trickle into your dreams as well, and give you an "embedded trigger".
The second problem is "hanging on" to the dream. I find that the lucid dreams want to fade (litterally the world begins to fade) and become non-lucid unless you concentrate on keeping them "focused". Actually putting your arms out, and spinning around seems to help for some reason, although the setting of your dream may shift, you can usually keep it lucid that way.
Has anyone else had similar experiences to this? (I haven't read all the posts yet, but I thought I'd throw my two cents in)