Do not use regular masking tape as it will pull off the paint. For fresh paint, use 3M Blue Painters Tape for Delicate surfaces. If paint over 30 days use regular 3M Blue Painters Tape. I hear the green frog tape is even better but have not used it. Don't buy off brand painters tape, it doesn't remove well and will pull paint.
It's good to run somethiing solid over the tape such as putty knife or whatever to assure even adhesion and do not stretch the tape.
Even when using the blue tape, when you go to pull it off after painting, pull from the area closest to the surface. Don't pull from a foot or two away as you go, keep pulling gently from near where it touches the garage. Otherwise you can still pull the paint off.