The following assumes that you mean "crank but no start". If you turn the key forward to the run position, you should hear the fuel pump turn on for about a second or two. *Immediately* after the pump shuts off, turn the key to crank it. Should start right up everytime. It's a common issue and nothing to worry about; doesn't necessitate fuel pump replacement. The fuel pump backflow valve is simply allowing the fuel to seep, or run back into the fuel tank.
If you simply mean, "no crank" then the easiest thing to do first is clean-up the battery terminals and make sure that the wires are in good shape; particularly where it grounds.