Here's a foolproof way to keep that under control. First, match up all your sheet sets, making sure the bed sizes also go together as well. If you are trying to get the most out of mismatched sheets -- let's say you have a good flat sheet whose fitted mate wore out long ago, and you've paired it with a fitted sheet whose mate also disappeared, and added a couple of lone pillow cases .... put that "set" together the same way.
2. Fold them immediately upon taking them out of the dryer. They will have fewer wrinkles this way.
3. Fold all the items except one pillow case.
4. Stack the folded items neatly, insert them into the unfolded pillow case, and tuck in the loose ends of this pillow case. Place this "packet" of matching sheets into the closet, shelf or drawer where you normally store them. You now have a set of matching sheets.
No more rummaging for matching sheets and pillowcases!
Do this every time you do the laundry and you will never have tangled-up sheet mayhem again when it is time to change your beds.