Step 1 Build a concrete "footer".
Start your masonry project by building a concrete "footer" using standard construction techniques. Use 1" x 4" or 2" x 4" lumber as form boards. Nail or screw the wood boards to 1" x 2" stakes hammered into the ground using enough stakes to keep the forms from spreading out when the concrete mix is poured into them. Another bit of advice is to keep the stakes below the top part of the boards so you can "Skreet" the concrete out nice and flat. Also try and keep the forms as level as possible. You'll need to determine the depth and width of the footer to your project accordingly.
Step 2 Apply mortar cement.
Now apply a good amount of mortar cement on the footer (Mix your mortar cement to the consistancy of oatmeal). Using a spirit level, lay and LEVEL the 1st Course of block or bricks WITHOUT SPACERS leaving a 3/8" mortared vertical space between each block or brick.
Step 3 "Butter" top edges of your block.
"Butter" both top edges of your block with about 3/4" to 1" of mortar cement. If laying bricks, spread about 2" of mortar on the center area of the row of bricks and using a brick trowel, separate the mortar into 2 lines.
Step 4 Place mortar joint spacers.
Using the CENTER of the masonry block or brick as a reference, place 2 mortar joint spacers on each side edge of the block or 1 in the center for bricks into the mortar.
Step 5 Place block or brick onto spacer.
Now place your block or brick HALFWAY onto the spacer and tap until it seats firmly down.
Step 6 Continue for each course.
Continue same procedure for each course, periodically checking for level and plumb of the wall.
Step 7 Scrape off mortar.
Using your trowel, scrape off any mortar that has squeezed out of the joint.
Step 8 Clean up mortar joints.
Now clean up the mortar joints by using a "tuck pointing tool" or a small length of rubber hose.
Step 9 FINISHED!
Nice and level without any "crushing" of the mortar joints.