Few things to do:
1. Keep the temperature under 200, 190 to 195 is best.
2. Be sure to have a fan cooling the extruded PLA.
3. Disassemble your nozzle and clean it really good and use a drill bit of the correct size to get any burnt PLA glued to the nozzle.
4. If your hotend have a PTFE tube that goes all the way to the nozzle, clean it often and once a quarter change it.
5. Increase your retraction settings so the PLA filament stays in the cold section of the hotend, anywhere between4 and 6mm.