if a girl likes a girl they often hold hands or kiss each other on the cheek in public. If they're open about their sexuality you may see girls making out on the sidewalk! Other times if it's at school for example you may see the usual kissing and cuddling or if the other girl doesn't know there will be a lot of staring.
ask her who she likes
Get to know her.
this is simple get to know this girl
If a guy look at the girl twice then it means she likes the girl
That means he girl likes you and answer that question by telling the girl something she likes to do. If you don't know what the girl likes to do then you're a goner
if she talks to you and touches you on the leg or something like that. then that means she likes you.
I gess the same way you can tell if a normal girl likes you.
Ask her.
ask her out
If no on likes you
go to 'ask' and type in 'how do you know if a girl likes you' you should find all you need there
just ask her if she likes you