Clean the plate first, every time
Fingerprints leave a film that plastic will not key into, and it builds up exactly where you grip the plate to flex a part off. Washing with warm water and dish soap, then drying fully, resets a plate more reliably than wiping it.
Isopropyl alcohol is the quick version between prints and it is worth keeping to hand, though it moves grease around more than it removes it. Use alcohol for a touch-up and soap and water when adhesion has genuinely dropped off.
Textured PEI keeps working long after it looks past it. A smooth PEI sheet that has gone glassy in one patch has usually lost its texture there permanently, and that patch will keep failing.
Nozzle height: squashed, not placed
A first layer should be pressed into the plate so the extrusions spread and fuse into a continuous sheet, with no gaps between neighbouring lines. A first layer that looks like tidy round strings sitting on the surface is too high, and it will lift.
Too low is its own failure: the nozzle ploughs, the extruder skips, and you get a translucent smear rather than a layer. The window between the two is smaller than most people expect, which is why the height is worth setting properly rather than nudging.
Bed temperature does one job
The heated bed keeps the plastic near the plate soft enough to stay bonded while the layers above it cool and pull. Too cold and the corners win. Hotter is not automatically better, though: an over-hot plate softens the base enough to deform it, which is elephant foot arriving by a different route.
Each material has a range for this, and the range is on its page here rather than repeated as one number that would be wrong for most of them.
Warping is shrinkage, and some materials always do it
A part that sticks and then peels a corner is not an adhesion problem, it is a shrinkage problem. The plastic contracts as it cools, the contraction pulls the corners inwards and upwards, and the bond gives way at the weakest point.
This is a material property. ABS, ASA and the nylons shrink enough that a draught across the printer is sufficient to lift a corner, which is why they want an enclosure rather than more glue. PLA and PETG shrink little enough that a clean plate is usually the whole answer.
A brim buys you more bonded area at the corners and costs a moment with the cutters afterwards. It is the cheapest thing to try, and on a tall part with a small footprint it is often the only thing that works.
