Position the concrete re-bar or reinforcement mesh. Set an expansion joint between the slab and the block. It also serves as a screed mark for the concrete. We also hired a contractor to complete concrete work for the slab. He poured the concrete in quarter sections starting at the back.
Some people prefer to give the slab small traction grooves by brooming the surface.
Brooming is also recommended for the apron. After the slab sections have set, place an expansion joint across the apron opening. You may opt to let the slab cure a day or two before pouring the apron, or pour the apron after the garage is built. Pour the apron with a slight slope. Finish the apron like the slab, except you may want to broom finish it deeper for added traction.