This is a bit long so get your coffee now
Skirting and preparing a fleece for sale:
Lay the shorn fleece out, cut side down. Tear off/pull apart with your hands any dirty bits of fleece around the back end and under the armpits, front and back - the wool here can be thick and greasy, like a sweaty dag
Pull off any tatty or very short bits around the edges to neaten it up. Check the belly wool, especially on a tups fleece - tear off any urine stained bits.
Cast your eye over the fleece - if it's covered in bits of vegetation, hay, thistles, burrs and so on it is not worth selling. If there is just a little and you can pick it off easily then it's fine.
Next check for soundness/tenderness of the staple - take a small bundle of fibres from the fleece, keeping them in the same order they were growing. Hold one end firmly in each hand and snap your hands apart a few times. A sound fleece will make a nice twang, whereas a tender or damaged fleece will try to pull apart and the sound will be weak - hold it by your ear to hear better.
Check for felting - gently see if you can pull the fleece apart, all over. Don't actually pull it apart, but grip with your hands as if to start ripping. A felted fleece won't budge, but with a nice open fleece you will feel that none of the fibres are stuck together. No-one wants an already felted fleece, even for felting (where you need to start by carding just as you do with spinning)
What is a good fleece? This depends largely on what you want it for. A fleece which is good for making carpets will not be the same good fleece for making vests, or for weaving fine suiting. It is though a good idea to see what sort of fleece you have before offering it for sale, so you can give an accurate description. Each particular breed has a fleece with particular qualities, so check your breed description or standard and compare your individual fleeces against that. Then you can sell it as 'typical texel fleece' or whatever.
However, for a general idea, look first at the crimp of the fleece - how many crinkles per inch are there along the length of the fibre ? How long is the fleece, from the skin to the tips?
Then look at the fineness. No-one will expect you to have had your fleeces micron-counted, unless you breed top-end Shetlands or other fine-woolled breeds, but you can give a rough idea of fineness. Take a small staple of the fleece, hold each end in one hand as before, but this time spread the fibres open, into a mesh. Hold this up to the light, or a dark background if the wool is white, and you can see if the fibres are fine or coarse. It helps to have something to compare them to, as most fleeces look fairly fine like this. You could try looking at human hair for comparison, your own and a baby's, say.
You can assess for softness by placing your flat hand on the cut side of the fleece with your eyes shut. Your finger tips are the most sensitive part of your hand so you can feel all but the finest fleeces there, and the middle of your palm is the least sensitive, so you will feel only a fairly coarse fleece there. Cloud-soft fibre such as angora and some alpaca cannot be felt at all, with any part of your hand, though you would feel it with your lips. If you bring your hand down onto a really fine fleece with your eyes shut, you cannot tell when you have reached it.
If your fleece has fallen to bits a little during shearing (usually when the sheep has struggled and got a foot in the fleece then kicked about, or has run away halfway through
) you can reconstruct it a bit by laying it out cut side down, then fitting it back together so it has all the right bits in the right place. Push it all closer together then roll and it should stick together fairly well. It certainly demonstrates that the fleece isn't cotted/felted if it falls to bits.
Roll it neatly, cut side out, and pack in a non-plastic bag, labelled with the breed, year shorn, sex of sheep and your details, plus any other info you want to include. When advertising, include a general description of the fleece, including colour, staple length, if it's crimpy, soft, robust (ie coarser), double coat and any other info you think would help a craft worker to select it.
If your fleeces are clean and well-presented your customers will come back for more.