I have seen this tip several times before but finally implemented it and I have to say it is so convenient and clean looking! All you have to do is neatly fold your sheets up to a rectangular size that will fit in the corresponding pillowcase. Neatly fold the other pillowcase and place inside. You will always be able to find the matching pillowcases and will know where each sheet set is at all times, all while keeping a clean organized look.
Here are detailed instructions on folding those annoying fitted sheets!