First of all, seasonally. So get spring summer wear out once weather gets a bit warmer, have some transitional pieces that can be worn all year round, pack away things that are very definitely winter weight.
Group things together in terms of all tops hung together, all dresses hung together - then colour co-ordinated, moving from dark to light - so all the blues together etc. Patterns are put in with the section where they have a predominant colour.
Bags grouped together, accessories grouped together, like scarves, necklaces etc so that I can see what I have for inspiration, rather than trotting out the exact same outfit each time. Shoes/boots/trainers at the bottom of the wardrobe. Separate drawer for sports kits.
Jumpers are folded and put on shelves, but not too many on a shelf or they get squashed and it is more difficult to pull out the one needed if there is a tower of other ones resting on it.
Trousers are usually hung up, jeans folded in drawers, Skirts go on a rail below the tops, but again always moving from dark to light coloured and grouped by colour.
Be interested to see what others do as most people have more clothes than they wear or need - I know I do! Do they rotate pieces in and out of the wardrobe or have a ruthless cull every so often? I am also guilty of keeping things that don't fit in the hope I will slim into them.