Best way is not to. If you monkey around with the ph level, you'll end up having sick and dying fish from the inevitable ph swings. It's a touchy thing. Your fish will adapt to the water conditions just fine. What kind of fish do you have? Some types prefer hard, alkaline water.
If this is a relatively new tank and the cloudiness is whitish, congratulations -- your tank is doing just as it should. The cloudiness will clear on its own after a week or a bit longer, and your tank will be much better able to handle the fish waste products than it was before the white cloudiness.
The three things you need to be testing for are ammonia, nitrite, and nitrate. These are the three factors most essential to keeping fish alive.
If the cloudiness is green, your tank may be receiving too much light, and you may be overfeeding. These factors can contribute to an algae outbreak. Cut the light and do regular partial water changes, and cut back on the feedings. Also, vacuum your substrate well.
If it's a brown cloudiness, your water may just be dirty. Do a good-sized water change and be sure to vacuum the bottom well.
When you do water changes, just be sure to dechlorinate it and match the temp carefully, within two degrees.