Most people ive found that play guitar don't know barre chords...
To OP
It will come with time man. If you want to make sure you have the transition down, play D to G back and forth as it requires you to move your fingers a long ways. Also just a tip from me. Practice playing open G with your 2nd 3rd and 4th fingers instead of usiing your 1st 2nd and 3rd. It will help on making the transition to an open C MUCH easier.
And to those of you wondering the note on the B string. Thats just the 5th of the G chord being played a 2nd time. If you play an open B, that is the major 3rd which is also a repeat. So either way works but the one where you play the 5th is called Folk G typically.
Btw my favorite chord is an Emin9 chord played using 4 open strings and the 5th and 9th played on the A and D strings. Listen to riviera paradise if you wanna hear it in full force. Strum upwards by the bridge and it will make girls throw up orgasms all over the place.
