Try to remember the regular endings, then keep in mind how they change depending on the group (-er / -ir / -re) and little by little you'll remember most of them. To be honest, I still check (usually online) when I need to be sure :P

Well, not all of them. You should focus on "le présent de l'indicatif, le passé composé, l'imparfait, le futur simple". The rest can be done later.