There are two common types of alpacas suri and huacaya. While both are available the huacayas are more readily available, and more easily prepared for hand spinning.
When choosing a fleece, start your observations as soon as you arrive at the farm. Is it clean and well kept? Does this farm know the value of the fleece? If you arrive to buy a fleece and find several years worth of fiber piled up in a loft or garage, be very cautious! Examine the bags and storage area to make sure it is free of any water or rodents.
To examine the fleece ask that it be removed from the bag by the seller. If it truly is a huacaya blanket, it will be in one or two large pieces. Otherwise, you are probably looking at seconds, which are completely useful, but do not command the price of a blanket.
Next, look at the empty bag, if there is a lot of dirt in the bottom, it is bound to be present in the fiber. While some debris is to be expected, donít buy a fleece that is too dirty. There are plenty of clean ones out there.
I also believe there are two main types of dirt. Hay and other vegetation versus just plain dirt. Believe it or not, I would rather have the dirt. By placing the fleece on a screen or in a mesh laundry bag and giving a good shake most of it is gone even before you wash it.
When selecting a huacaya fleece, look for a nice staple length. As you gain experience as a spinner you will develop your own preferences, I prefer a long staple of around 4-6 inches. With alpaca fiber a longer staple length is preferable if you intend to spin the raw fleece as it is more slippery than wool.
Another characteristic to consider is the crimp. Huacaya fiber is very uniformly crimped. If there are fibers in the fleece that have no crimp, these are guard hairs which are undesirable in a hand-spinning fleece. To remove the guard hairs, the fleece must be placed shorn side down and the guard hairs plucked out of the down fleece. If you select a guarded fleece, be prepared for more work, but they can produce an unexpectedly lofty yarn. Avoid paying for the guard hair by asking for a discount on these fleeces.
Be sure to check the shorn side for excessive 2nd cuts and the tips for matting. Both of these can affect the quality of your finished yarn.
One final note, do your research. Do not go to just one farm. Check with your spinning guild or through the local extension office to get an idea of the local price for fiber, as is does vary by area.