Unclog
This will be a guide for a basic unclogging procedure. You would want to unclog your hotend if debris such as dirt has entered your hotend.
Procedure
This procedure will explain an unclogging procedure for PLA. Adjust the temps to something appropriate for your material.
1. Heat the hotend to 200C
2. Extrude 10mm of filament
3. Let it sit for five minutes at temp
4. Lower the temperature to ~85C
5. Let it sit for five minutes at temp
6. Loosen your extruder tensioner
7. Pull the filament out
If it is ABS, soaking the nozzle in acetone can also help.
Prevention
Filament Cleaners
basic: https://www.youmagine.com/designs/universal-filament-filter
for mounting on an extrusion: https://www.youmagine.com/designs/aluminum-extrusion-filament-cleaner