Wow there are some great things that have been said. I will just add my two cents.
Practically all of my posts of this forum are the same because usually every problem having to do with lucidity (or the lack thereof) have to do with the basics.
So pretty much the basics are:
1. Get enough sleep every night (it depends on the person, but its anywhere from 6 to 8 on average)
2. Write in your dream journal every day (yes, every day)
3. Do reality checks during the day when convenient.
4. Dont worry about it too much. It will come in time.

I promise that that if you do these 4 things you are guaranteed to have a lucid dream. Seriously. Its science man! I applaud your tenacity. It took me 8 months of hard work and being consistent. I was extremely consistent for about 3 months when I finally had my first LD. YOU CAN DO IT!