I find it best to unload the filament by heating the extruder up to temperature then after the temperature has been reached press down on the filament tension arm and then push the filament down (feed the filament by hand) until at least 1/2″ has been push through the extruder then immediately pull the filament out. Unloading the filament this way helps remelt the end and get rid of the bulge that may have formed which can get caught between the pinch wheel and bearing as you pull the filament out. If this happens and the filament is hot enough the end may get broken off and left behind causing a blockage that may require taking the fan off the extruder to clear.
More explanations from Jetguy:
Since you asked about unloading filament, here’s the answer:
PLA generally tends to get brittle overnight when it is curved on the spool and then straightened in the guide tube or path in the extruder. It might crack in the end right above or in the extruder the next day. ALWAYS extrude before unloading. In other words, on the i3, preheat, wait for it to reach extruder temp, I manually push down on the filament into the extruder and extrude at least 10mm of fresh filament, then press on the release lever and rapidly pulls up the filament while holding the release lever. ALWAYS cut off the melted tip before inserting the filament the next day.
Again, I cannot stress enough, ALWAYS, as a rule, a habit, even as a metal tick, extrude BEFORE removing or unloading filament. Do not power remove filament using the menu. Remember, you have MOLTEN plastic on the end of the filament. If you run that up back through the drive gears with the ilder bearing pressing against it, it will deform and might snap off inside the extruder between the drive gear and the lower plastic guide. Failure to follow this can lead to a major jam that requires taking apart the entire drive feed system.
The whole reason again I push down on the lever and manually extrude and then manually pull back, I can feel what the filament is doing. If when pulling back I feel resistance, i know i need to extrude MORE fresh filament before pulling back out. If you fail to do this, you likely will pull up molten plastic that always gets caught in the worst possible place in the feed mechanism and then you are having an even worse day.