Proper drainage and a level surface are important when building a paver-patio.
When designing a paver-patio make sure to account for proper drainage across the structure. Building the patio at a 1-2" slope away from the house will ensure that water and precipitation drain away from the foundation and do not pool up under the brick pavers and soak into the basement or lower level. Grading the dirt with a slight slope toward the yard should give the proper drainage. A gas-powered compactor can help tamp down and level the dirt and lower it more to direct the water to the preferred places.
When laying down sand to place the brick pavers, use 1" conduit pipes to create rails so there will be a smooth and level surface to start laying the brick. Place the 1" pipes just inside each of the edges where the patio will be and then get a 2'x4' that is long enough to reach across both pipes. Pour the sand as evenly as possible over the conduit, taking care not to bury them. Get someone to help you drag the 2'x4' across the top of the conduit pipes, smoothing and leveling the sand along the way. Do this for the length of the patio, picking up and moving the rails as necessary to keep a 1" level sand base to work with.
Get the foundation stones (the ones on the very bottom) as level as possible to begin with by using a bubble level across the connecting stones. If the bottom stones are not level any mistakes made will become more and more amplified and noticeable as stacks are built. If you find some stones are minimally higher than others use a rubber mallet to pound the high points down a little bit until they become level. Low stones will have to be lifted and sand added beneath them to bring them up to level.
Once the first level of pavers is laid and the stones are level with each other, it is time to fill in with sand. Pour a thin layer of sand over the stone pavers and sweep the sand into the cracks with a broom. As the grains settle and moisture reaches it, the sand acts as a natural cement, locking the blocks into place and solidifying the work.
If a 90-degree angle is wanted at the corners of the paver-patio, cut the stones at 45-degree angles using a circular saw and a diamond blade. For the first level of stone simply cut the angles and fit the two corner pieces together and lock them in with sand, but it becomes trickier on the upper levels of the patio. Custom fit pieces of stone may need to be cut to keep from having gaps in the corners. These small pieces can be glued in with a block adhesive, which will prevent the smaller pieces of stone from popping out of place. Use the block adhesive generously in and around the corners, as these are the most vulnerable parts of the patio.