One of the MAIN factors you could had received a diluted result was because your creataline and PH levels were too low. The faster the fluids flow through your body, the more the levels decrease. Labs test for these factors to determine if a sample was diluted. One way to fix that is to load up on creatine 2-3 days before your test. On the day of the test you want to eat tums/rolaids/salt every hour to increase specific gravity levels. That should help avoid a dilute test.