What i like to do is to tab out the first couple lines of the song, then figure out what (if any) flats or sharps there are. Then i google "circle of fifths" (because i can never remember what keys have what sharps/flats) and find out what matches it.
Quote by nico_9550
I'd like to know how to recognize in which key a song is in, if anyone could help me out

Key of the song = Scale used in the song.
I usually figure out the chord progression, then figure out what scale it's in.
you're a stone fox
Listen for where it resolves
But boys will be boys and girls have those eyes
that'll cut you to ribbons, sometimes
and all you can do is just wait by the moon
and bleed if it's what she says you ought to do
A basic way to figure out what key it is in is to figure out what chord it resolves to. Listen for when it sounds "finished", that there's no more tension, then figure out that chord. There's a good chance that if the song resolves to a C major chord, the key is in C major. If it resolves to a D minor chord, it's in D minor, and so on. Just listen for the resolution.

EDIT: Hydra kinda beat me to it.