Engine light shows on dash wile engine is running

First thing i do is clear the codes by unplugging the computer / ecm or even on some cars just the efi relay for a few minutes this will reset the codes

however if it comes up again and the car seems to run fine you should definately go to your mechanic

some manufacturers can tell the problem with the car just by plugging in thier computer however most small mechanics just use a code reader these are good too but sometimes get confused with multi codes