The standard advice is to take everything out, try it all on and be ruthless. It works for some people and defeats most, because it turns a vague unease about having too many clothes into an exhausting all-day project with a mirror involved.
Turn the hangers round
Hang everything facing the same way. When you wear something and put it back, hang it the other way round. After two or three months the wardrobe has sorted itself into worn and unworn without a single decision being made, and the result is usually uncomfortable reading. No judgement required, just a record.
Separate unworn from unwanted
Things go unworn for different reasons and they need different answers. Something that does not fit is a decision about whether you expect that to change, and keeping one size either side is reasonable while keeping four is storage. Something that needs a button or a hem is not unwanted, it is waiting, and it belongs in a small pile with a deadline rather than back on the rail. Something that fits and is fine and still never gets picked usually fails on comfort or on how it makes you feel, which is a legitimate reason to let it go and one people argue themselves out of.
Deal with the mending pile honestly
A mending pile with no date is a donation pile that has not admitted it yet. Give it a fortnight. Anything still sitting there goes, because three months of experience says it is not going to happen.
Store out of season properly
Taking winter coats out of the wardrobe in spring frees more space than any amount of reorganising, and it also protects them. They want to be clean before storage, because moths are attracted to the traces on worn clothing rather than the fabric itself, and they want to be somewhere dry rather than vacuum-packed if they are natural fibres, which crush and stay crushed.
Hanging against folding
Knitwear stretches on a hanger and should be folded. Anything that creases badly should hang. Everything else is a question of which you have more room for, and shelves hold roughly twice as much as a rail in the same space if the piles are kept shallow enough to see.
Where it goes
Decide the destination before the bag leaves the bedroom, or it will sit in the hall for a month and some of it will quietly come back. Charity shops want clean, saleable, in-season items. Worn-out textiles are recyclable at most council sites even when they are unwearable, which is better than binning them and removes the main excuse for keeping something ruined.