I know it's frustrating, but you just need to keep at it. It takes some people more practice than others before becoming lucid. There's no sure-fire way become lucid every time.

I'd try becoming more aware of your surroundings in waking life. Pay attention to details, and if anything a little strange happens, be sure to question it and don't brush it off. By being more aware in reality, you may become more aware while dreaming and be more likely to obtain lucidity.