Handspun yarn can be a challenge to knit or crochet with. For starters, if you are working with a single ply yarn it will most likely have a lot of twist in it. This means that it will curl back onto itself and can have a mind of its own. Remember - spinning yarn is basically applying twist to the fiber in a single direction in order to bind it together. This creates a lot of stored up energy in the yarn that is just dying to get out! One way to deal with a really twisty single skein of yarn is to soak it in warm water for a while and hang it up to dry on a hanger. You can weigh it down a bit with a towel hung through the bottom. Be careful not to use too much weight or it will ruin the texture of the fiber and stretch it out too much. If you have a spinning wheel you can also run it back through onto a new bobbin in the opposite direction from which it was spun.
2-ply is by nature a more balanced yarn because it is comprised of two single strands of yarn spun together in the opposite direction in which they were spun. This evens out the energy stored in the individual strands. It is also stronger and less prone to breakage. If you are having trouble with a single ply, you might want to try 2-ply or Navajo (N) ply yarn.
2 Ply Handspun Yarn
In any case, if you are knitting or crocheting with handspun art yarn, try using a bigger hook or needles. This will show off the texture of the yarn and give it space to move.