Maintain your pool water level halfway up the skimmer box opening.
A pool may typically lose a minimal amount of water each day (no more than ¼ inch) due to evaporation and/or splash out. If your pool is losing more water than that, there could possibly be a leak. Monitor closely and consult your pool professional if you suspect a leak.
Loose tiles or cracks in the pool deck may be an indication of a leaking pool.
Cracks and gaps in the bond beam may be an indication that your pool is leaking.
If you notice water-saturated soils in the area around the pool, pool pumps or plumbing, your pool may be leaking.
If you see bubbles in the return water when the pool's pump is running, it's likely there's a leak in the suction side of the filtration system.