There are many degrees of Dry Eye so there are many answers to this question! For some people it's perfectly OK to just use an artificial tear when there is a little bit of discomfort. Feel a little dry? A tiny bit of scratchiness? Go ahead and put a drop in.
Other people have Dry Eye symptoms all the time. The doctors at Skyvision like to tell these folks that they should use their tears just like they were a prescription medicine. 2, 3, sometimes 4-6 times a day on a schedule is sometimes what it takes to be comfortable with your Dry Eye.
It turns out that it is usually easier to prevent the Dry Eye symptoms from starting than it is to stop them once they start! In other words, the time to take your eye drops is when you DON'T have any symptoms. If you wait until your eyes feel badly it's already too late.
Think of an image of a well with a bucket that hangs down into the water. If the well slowly drains all day long pretty soon the rope won't be long enough to reach the water. In order for the bucket to get to the water you first have to FILL UP THE WELL! Same thing with dry eye; if you don't keep the well full all day you won't get the benefit of the tears until you fill the well (your eye) back up!
Ask Dr. White, Dr. Schlegel, or Dr. Kaye what kind of artificial tear is best for you, and how much to use them.