Some phrasal verbs are separable, and the object can go either after or between the parts of the phrasal verb. You just have to learn which phrasal verbs are separable or not. There's no trick to finding out.
The main rule to remember is, if you have an object pronoun (me, you, it, him, her, us, them), it always goes inside the phrasal verb: turn it off, turn it on, and so on.