Level footings are the key to success. Unlevel footings cause unnecessary work when stacking, and extra time to correct problems.
C-hooks or rebar dowels should be installed every six feet along the center of the wall and at all corners. (Check local codes for compliance.) The second course of blocks is tied to the C-hooks or rebar dowels.

Measure the footings to the exterior dimension of the building and mark with a chalk-line. Fasten a 20 gauge L-shaped sheet metal for the blocks. When several rows of block are in place, go back and install a similar guide on the inside of the wall, being sure to push the blocks against the outside cleat for stability.

Be sure to pin, square and chalk all corners before starting walls. Then, for ease of handling, move all materials inside the perimeter of the building.

To simplify step footings, build them to the height of a block ... 16".