To properly pinpoint a pipe or conductor using a Pipehorn pipe and cable locator, you want to hear the signal fall off on both sides of the conductor. You will either get a balanced signal, meaning it falls off evenly on both sides of the strongest signal; or an un-balanced signal, meaning it falls off faster on one side vs. the other (as shown below). An un-balanced signal usually means you are picking up more than one conductor.
If the receiver is beeping, you need to turn the gain down. This will allow you to narrow the gap. You also need to keep the receiver level during pinpointing; do not swing the receiver during pinpointing.
When locating on a steep hill or bank, you want to still try to keep the receiver as level as possible, otherwise you will miss your mark as shown below. Remember that your strongest signal comes from when the sensor is closest to a conductor. This may not be straight down on a hillside, but off to the side.
The deeper the conductor is, the worse this problem becomes.