Basically, you need to practise them, and always use them in a full sentence. Avoid the dictionary definitions and lists, because the meaning depends on the context of the full sentence.
Some phrasal verbs are separable, and others are not. You just have to learn which ones they are. However, when you use an object pronoun (me, her, them, us etc) with a separable phrasal verb, the pronoun always goes between the two parts: turn it up, tell her off, think it over...