I'm not sure what you're asking. Do you need tips on how to sing them or how to recognize them?
Only play what you hear. If you don’t hear anything, don’t play anything.
-Chick Corea

Just practice, practice, practice dude. I couldn't get the hang of them until I starting singing in a large vocal group.
well firstly..try to imagine the note before singing it...as far as hearing it and knowing what it is..takes alot of ear training..thats past my expertize lol...it took me awhile before i could do scales and little trills and stuff..that just takes time...

if you sing to what you play on guitar some good things to do are star wars theme and stuff like that..thats what i do..im pretty good at star wars..without the guitar..maybe ill put it on my profile..LOL