It's through practice. As native speakers we know intuitively what sounds right and appropriate, if the tense isn't obviously wrong (for example, there's no reason to use future forms when talking about the past). The grammar rules that you learn are a result of analysing what sounds right to us. If you're learning English properly, you'll learn many very clear rules about which tense is right in which situation. Of course, if there is a specific example which confuses you, by all means post it here.

practice - practice - practice. Whenever I get the chance I will go to a Spanish restaurant, I went to Costa Rica last year to practice, I watch TV, I spend time on the internet learning Spanish, Get more involved.

If we train enough we'll use tenses correctly by no time wasting.

1. Get more exposure to the target language; this can include written and spoken texts. 2 Practice, practice, practice (speaking and writing).