The first layer is where every print is won or lost, and for the longest time mine was won or lost more or less at random. I would level the bed with a sheet of paper, get a print that looked perfect, then come back two days later to a part that had peeled off the plate in the first five minutes. Nothing had changed. That is the maddening part. Nothing had changed, and yet everything had.
The paper method is fine in principle. You move the nozzle to each corner, slide a sheet of paper underneath, and adjust the wheel until there is a slight drag. The trouble is that "slight drag" is a feel, not a measurement, and your feel drifts. Four corners means four judgements, and by the time you are back at the first corner the bed has moved because tightening one wheel tilts the whole plate. So you go round again. And again. It is the printing equivalent of trying to balance a wobbly table by sawing the legs.
Two things finally settled it for me, and neither was clever.
The first was a glass bed and a proper heated plate that actually held its shape when warm. A lot of my drift was the stock bed warping as it heated, so a level I set cold was simply wrong by the time PLA was going down. Levelling at temperature, on a surface that did not bow, removed an entire category of mystery.
The second was a BLTouch. I resisted it for ages because it felt like papering over a mechanical problem with electronics, which it partly is. But a mesh probe measures what the bed actually does across its whole surface, including the warp I could never feel with paper, and then the firmware compensates as it prints. The honest truth is that it is not solving levelling at all. It is solving the fact that beds are never flat and my fingers are not a measuring instrument.
If I were starting again I would still learn to do it by hand first, because when the probe misbehaves you need to know what good looks like. But I would not pretend the manual method is anything other than a skill you have to keep paying for. Measure the bed, let the firmware do the arithmetic, and spend the saved evenings actually printing things. The war does not end. You just stop fighting it with paper.