Lay out the footing with STRINGS FIRST. Set up a batter board so that you know how DEEP you have to dig the footing trench, NOTE that if you are in an area like the NORTHERN States, you must put your footing BELOW the frost line otherwise it will heave, i.e. the FREEZING action of the water in the soil will BREAK your concrete footing.
REMOVE the black organic or brown organic soil. Dig down to MINERAL soil or gravel. Set up forms to size, level them using the DEPTH or HEIGHT reference from your LEVEL BATTER board. SQUARE the footing forms off, do a NICE JOB.
Pour the cement. For footings you should use 2000lb.concrete.
When set, after 24 hrs. remove your forms, lay out the exact position of the wall to be built on it, and snap marks with chalk lines. Bang in a concrete nail, right INTO the new concrete and attach lines in the correct places.
SET UP your corners first. Use about 1/2" of mortar under the first row of blocks and tap them DOWN to level, using a torpedo type level that indicates level in 3 directions. FROM those corners that are NOW set up, use block lines and lay the first rows PERFECTLY straight, to your PLAN.
Move the lines UP to the TOP of the NEXT block, and lay the second row EVEN with the TOP of the LINE. Make sure the lines are pulled VERY taut so there is NO SAG in the middle.
Butter the blocks and tap them so that you have about 1/2" mortar lines both horizontally and vertically. A tiny bit of variation means nothing.
Remember the rule, lay two over ONE, one over TWO centering the blocks so that your joints are staggered for the second ROW. ALWAYS make sure there are not two blocks directly over one another, it will be a weak spot in the wall.
Level EACH course as you go, do NOT allow errors to accumulate.
ALWAYS use your mortar before it gets too dry. If you are using CLAY type blocks or bricks, make sure you soak them for a few minutes before you apply mortar, otherwise the clay will suck the water out of the mortar, and you will have no bond.
If you are using concrete blocks, it doesn't hurt to spash THEM with water before you lay them also if the weather is hot.
When you lay the blocks, clean up as you go, smooth the joints, and if you are planning more than 3 layers of 8" concrete blocks, it's best if you put a reinforcing MESH at the corners. Lay the corner MESH right directly ON TOP of the corner blocks, and flop mortar hard on TOP of it, and then place the next BLOCK on top of that mortar right away.
If you are going more than 3 rows, it's best to do the NEXT 3 rows the second day, give the first rows a chance to set up.
When your wall dries, fill to grade CAREFULLY with GRAVEL or sand, NOT clay or topsoil.
If you have a whacker-packer, which you can rent, you can pack the layers of gravel adequately to proceed with your slab, but OTHERWISE, WATER the gravel down and that will help settle it. If you have to use poor quality fill, don't build the slab on top of it for at least a YEAR, otherwise it will settle UNDER the slab, and the slab will crack. Level the soil and water it down if you can. Add more soil as it settles.
When you build the SLAB, make sure you put POLYETHYLENE under the concrete slab to prevent water seeping UP, and use concrete wire mesh 6" and also use reinforcing steel BOTH ways on 1' centres--especially if you are going to drive a vehicle ONTO that slab. CONCRETE has excellent compression strength, but very poor TENSILE strength, which means you cannot put weight on it UNSUPPORTED unless you have TENSILE strenght built into it, like reinforcing rod.
Pour the concrete, get lots of help, it's heavy work. Level the concrete and get a spinner to smooth it out perfectly, level and polish it.
Have fun! Ignore any minor defects, for someone that never did it before, it will probably turn out just fine!