This advice is very good: https://english.stackexchange.com/questions/25038/phrasal-verbs-rules-and-tricks It talks about common themes, and says: Off often conveys a sense of surprise or something being out of control (go off (=explode), set off, let off (both=cause to explode), make off (=run away), make off with (=steal), ) •On often conveys smoothness or harmony (get on (=have good relations with one another), or continuation (go on (=continue, proceed), carry on (=continue)) •Up often conveys a sense of something being finished or completed (eat up, drink up, settle up) or of inclusion (count up, make up (=comprise)) or of creation (make up (=invent), dream up, set up) •Out also often conveys a sense of something ending, but in a premature or undesired way (fall out(=cease to be friends), drop out (=leave/be expelled), wipe out (=fall off, e.g. a surfboard)). But you're right, lots of them you just have to repeat repeat repeat!

For me, the best way to learn phrasal verbs is to make up sentences containing them, as many as you can, and sometimes write little essays using these verbs as much as possible. Say, you've just learned the meaning of "go off" - take a pen and a sheet of paper and compose some sentences with this word. For example: "His alarm went off at 6 am but he didn't wake up"; "They were told the bomb was timed to go off in 15 minutes"; "His gun failed to go off", etc. Such practice helps your use of English and helps to memorize these verbs.

I also think that using them in practice is the best way how to remember them! You can either make up sentences as it was mentioned above or you can for example learn one phrasal verb in the morning and focus on it the whole day - try to use it, try to think about it as much as possible.

Good resources: "English Grammar in Use" (Cambridge, Murphy) and "Phrasal Verbs in Use" (Cambridge)

Yes, I believe they are just the sort of thing which you lose if don't use. Just take yourself back to how you learned the phrasal verb "get up" for example. How many times did you repeat it? How many sentences, rhymes, and probably songs with it you listened to and repeated?