My checkout lady at my local supermarket shared this great tip. Cut a piece of straw and thread it onto your chain, then do up the clasp. This is great for travelling. Pop your chain in a snap lock bag or draw string organza bag and you will never have to worry about knots in your chain again.
The second great idea that I use in my studio for storing many chains comes from Andrew Berry from At The Bench. Pop your chain in a small zip lock bag leaving a small tail of chain dangling out of the bag. Zip up the bag to hold the tail in place. There is no way this chain will tangle now!