How do you remember how to conjugate for each tense?

The best way for me to personally learn and remember is by creating/ noticing patterns. There will always be a pattern with conjugations, even for the irregular verbs. For example, present tense endings I say to myself "o, as, a, amos, aís, an". For imperfect it will either be -ía or -aba (my teacher would always tell us to think of a Swedish pop group: Abba). The most effective way for me would be to continuously write out the conjugations and notice which verbs conjugate in the same way. This allowed to visually see patterns as well as learning how to spell and pronounce the words. 

However ultimately the best way to strengthen any section of language learning is through practice, do not worry if this takes time, repetetion is normally the best way to ensure you truly understand and take in what you are trying to learn.