Singing and Playing

It took me a while to get the hang of learning to play and sing, (guitar and piano)

Its mostly rhythm syncing...
Usually, especially with guitar, there should be dwon beat strum that helps syncs the rhythm,
try tapping your foot to notice where all the beat points are in the pattern, than drop the instrument and sing while tapping your foot,
then just slowly put it together...
it also helps tremendously if you practice the shit out of them both seperately...
BUT BECAREFUL!
theres a catch into learning how to play and sing efficiently, and thats when your only doing one, you start to suck...
that happened to me when I got to use to playing and singing, whenever I was just singing, like in the studio
My rhythm and sometimes my pitch would be off, because I wasn't playing as well, and I had to relearn songs seperately