One of the most important things in maintaining your pool is keeping the water at the proper level.
For most pools the correct water level is at the middle of the tile.
Find the skimmer opening (somewhere along the tile line) and ensure the water is at least half way up the opening. Improper water level can cause your pump to run erratically or not at all. If you will be cleaning your D.E. Filter, add an extra two to three inches of water for the backwash cycle.
I recommend attending to this step first because you can turn on your hose to add water and your pool will be filling while you move on to cleaning or other maintenance tasks. If you plan to add water while you are in your home, remember to turn on a timer or alarm. Once inside, it is easy to forget that your pool is filling.
On to Step 2: Test Water