Plan your patio. Decide where you'll put it and how big it will be. Take the size and shape of the concrete slabs you're using into consideration.
Clear the area where the patio will be. Remove plants, bushes and trees. Use stakes and line to define the future patio's edges.
Dig out the soil inside the stakes to a depth that's about 1 inch deeper than the thickness of the concrete slabs you're using. Flatten the soil with a tamper. If your patio is next to the house, make a slight grade so that water will run off, away from the house.
Pour 1 inch of leveling sand over the tamped earth. Stretch a string from one boundary to the other to gauge the flatness of the sand.
Start laying the concrete slabs in the center of the excavation if they're irregular. Fit the pieces together as you move outward from the center. If the concrete slabs are intact and square or rectangular, start at one side and work across, then down. Level the sand if it's disturbed.
Adjust your patio design to accommodate the slabs so you don't need to cut any of them. If you find that you do need to make cuts, use a diamond saw blade.
Dig a trench around the patio if you want to add edgers. The trench should be as wide as the edging bricks and deep enough for the bricks to be even with the patio when they're laid on top of leveling sand. Add the sand to the bottom of the trench, flatten it and install the edgers.
Rinse pea gravel or sand into gaps between the concrete slabs.