Drywall screws and alignment for ceiling

[vdotmatrix]

1. I am putting up 5/8" type X drywall in the garage ceiling (which I just insulated with R-19 CUZ it is also the masterbedroom floor) and I want to know what size drywall screws I will need. I am only doing half the garage right now 12x12.

2.the 4x8 sheets of drywall will not always have to line up perfectly on the joist RIGHT?

Is there a formula?

The joist although sorta evenly space aren't always at 15" or 16" apart.

It's sometimes better to be lucky than smart.

[HayZee518]

Use 1 X 3 furring strips fastened 16 inches on center to the joist face. This way you'll have a fastening system for a screw every 16 inches.
"zero - 16 - 32 - 48 - 64 - 80 - 96.
For 5/8 inch rock I'd use fine thread #10 X 1 5/8 long screw every foot