No long essays, just solutions. Try these first before you Google for an hour.
Clean the bed with isopropyl alcohol. Check bed leveling. Lower the nozzle by 0.1mm.
Retraction: 2-4mm. Travel speed: 100-150 mm/s. Wipe nozzle after retraction.
Bed too cold. Enclose the printer. Use a brim. For ABS, keep the enclosure closed.
Check nozzle clog. Clean the extruder. Make sure filament isn't tangled.
Belts too loose. Print speed too high. Check for obstructions on the axes.