1.
Have several meanings (like
other words) E.g. go off = start making a noise (an alarm); go off = explode;
go off = leave/go away.
2.
Sometimes the meaning is
literal (you can guess it from the verb and particle. E.g. go off = leave; take
off = remove, etc.)
3.
Mostly, the meaning is abstract
/ idiomatic; you have to guess it from the context. E.g. go off = take place /
happen; take off = start flying, etc.
4.
A good dictionary is needed to
help oneself identify the appropriate definition of a phrasal verb as they can
transmit its action to an object (Transitive=T) or they cannot transmit its
action to an object (Intransitive=I)
5.
When the phrasal verb is
transitive, it can be either separable or non-separable. In separable
phrasal verbs, the object CAN separate the phrasal verb OR
come after it.
E.g. Throw away
Throw the banana peel away / Throw away the banana peel
Throw the banana peel away / Throw away the banana peel
But if the object is a
pronoun (object pronoun, of course), it MUST separate the phrasal verb.
Throw it away.
Throw it away.
In non-separable
phrasal verbs, the object always comes AFTER it. E.g. could
you deal with the problem? / Could you deal with it?
E.g. My boyfriend gets along with my parents / my boyfriend gets along with them.
SOURCE: Inside Out series, Upper-intermediate. Macmillan