If I do a reality check (and let's say it's real life, and I'm not dreaming) and fail the dream test, should I openly say/think: "NO. I'm not dreaming".

For me the repetitive nature of RC's is what causes the imagery to show up in dreams. So, It does not matter what you say in your waking hours, IMHO.

Is it good to do one reality check, and then right after that one do another?

Yes... again repetition is good

Should I leave my TV off? Will it influence my ability to achieve a lucid dream?

Sound can keep you semi-grounded in your waking life. However light is the enemy of sleep.


How long do you think it shall take for me to have my first lucid dream?

If you study the sleep and dream process, gain confidence that it will happen, and try a variety of techniques it could happen at any time.

Good luck!