Questions about tense

Hi there

Tense has always been a pan in the ass to me.

Like when a person says: you are smart to have noticed it and if I use a phrase like that, I would definitely say: you are smart to notice that. or its smart of you that you noticed that.

I really have difficulties when it comes to tense. have done/ had done/ did. or even present tense.

I have already checked it up ( like now, or should I use already checked it up) in grammar books, I know the principle basically, but usually when it comes to choosing a correct tense, the intuition is the only thing I can rely on.

Many thanks