When you come home, fish around in the inside of the ball of yarn to find the end.
Pulling the yarn from the middle of the ball will prevent the ball of yarn from rolling all around the floor as you knit (to the great disappointment of your cat).
If you pull out a ton of yarn, wrap the extra around the ball of yarn for now.
If you remove the yarn label, keep it. You can put it in a special folder or zip-top bag for yarn labels, or even store the information digitally on Ravelry (the site that you really should know about anyway).
This just ensures that you'll know what you bought in case you want more, and is a habit that will save you from grief for years.