To select the pump which will best suit your purposes, you need to know your pressure requirements: How much pressure do you need to generate in order to transfer a volume of fluid from point A to point B?
Knowing how your pump sounds when it's running healthy can save you a lot of money in the future. Every pump will make a “healthy” free flowing sound as a medium is passed through it unimpeded.
If your pump has low flow or head pressure, or is performing erratically, you need to find out what the issue is quickly. One common problem is that a pump is not receiving the right amount of power.