Most dab pens are easy to clean, and ovens can be wiped out with a Q-Tip soaked in rubbing alcohol. You may be able to soak the mouthpiece in a jar of alcohol, but be sure to check the instruction manual to see if you can, and for other cleaning tips.
Some people clean their dab pen after each bowlful of concentrate has been completely vaporized, but at the least, it’s recommended to clean it out at the end of each session. It’s a good idea for the oven to be a little hot when you wipe it down, but not at a high temperature.
Dabs can be sticky so it’s important to clean your dab pen regularly to ensure it functions properly and has a long life.