Everyone always gets this wrong.

Right...

Move the weight backwards until the tone arm is "floating" horizontally - ie with no downwards force at all.

Now move the number dial round WITHOUT MOVING THE WEIGHT so that it is set at 0. Horizontal wightless tone arm should always be 0

Now turn the weight and dial so that it moves up the tone arm. Each incremental number (1,2,3,4) represents a gram of force on the stylus.

Most stylii want around 4g of tracking weight. If you are unsure check the manufacturers website.

Too much tracking force results in shitty distorted sound, it damages your records and your stylus. Too little force and it will skip.

If you are playing outdoors or somewhere where you need more tracking for whatever reason give it an extra gram or so.