Gascolater check
There's also the drain on the gascolater to check, just forward of the port wing leading edge. You won't get a flow here unless the fuel selector is selected to a tank - some pilots turn it to'off' after a flight, so check it's got the LOWER tank selected (ready for startup)
An essential point with all these tank drains (we've got FIVE of the little darlin's on our PA28-151) is to make sure they're seated back properly once you've done the check. We had to buy an expensive new tyre when one dripped onto a wheel and ruined it. Even more critical is the aforementioned gascolator drain. A serious crach has occurred in the past when the engine failed on takeoff due to some of the fuel leaking out of here...
The Odd One