How do you mark ceiling joists?
Similarly one may ask, what does a ceiling joist look like?
A ceiling joist is a horizontal member that spans across your ceiling, used in framing to span an open space. These run between beams and transfer the load from your roof to the vertical members or studs.
Similarly one may ask, do ceiling joists line up with wall studs?
If you use stack framing for your trusses and wall studs, then it helps a lot to use the same spacing on your floor joists, so your wall studs can line up exactly with the floor joists. You can probably find in somewhere in the code that you can use 16, 19.2 (you said 19-6)or 24 inch spacing legally.
Fine Homebuilding notes that 2-inch by 6-inch garage joists will support a weight of up to 50 pounds per square foot. If you overload your garage's ceiling joists, the ceiling may appear to sag from the strain. While your 2-inch by 6-inch joists can collapse from too much weight, such a scenario is uncommon.