While you are climbing, glance periodically at the vertical speed indicator. If, based on the current conditions, the climb performance is consistently lower than what you have come to expect at a specific airspeed, make sure there is no additional drag. You may have forgotten to retract the gear or flaps. But if your climb checklist is complete and your airplane still fails to perform as expected, turn around and visit your mechanic. The good news is, you should still be close to the airport, which, if you’ve already gained sufficient altitude, makes it easy to turn around and get down on the ground before the airplane leaves you with no choice but to do so.