Assuming that we know it has gas in the tank...

Sounds like a fuel pump or plugged filter to me.

Check the filters first:
Do you have an inline filter? Try removing it and blowing through it. Is is plugged? How about one of those little screen filters where the line comes into the carb? Remove it and see if it is plugged.

Then worry about the fuel pump:
Shadetree method: You could remove the output line from the pump and stick enough fuel line rubber tubing on it to run into a can, bottle or something, then crank the engine and see if you get any fuel out of it.

The right way: Don't the pro's use a device that they can connect to the fuel line that will measure pump pressure?

If all this fails, suspect the sock in the tank.

One other thing... If you are running gasahol it has a nasty habit of cleaning everything up, and dumping all that residue that it strips from the tank and lines right into the filters. Nice to have a clean fuel system, hard on the first couple of filters.

Don't lose your head to save a minute,
You need your head, your brains are in it.
Burma-Shave (1947)