I think most of the important bits have been covered by now. The only thing I'll stress is stay active! if you let it get hold, and just stay in bed all day, or lounge around the house it will only get worse. Also I find its really important to get out of bed at a reasonable time every day. This can be really difficult if, like me, you feel truly horrible in the mornings. Generally I find that if i get up at around 9ish and move around the house, I feel a lot better than if i sleep in till 11ish. The easiest way Ive found to do this is drag myself out of bed and have a shower- I usually feel instantly better.
My sympathies to JESSHOLMES, I got a really bad case of glandullar fever halfway through my second year at uni, and still have PVFS 3 years later. On the plus side I have found myself a good GP, who told me that PVFS lasting up to 5 years can be fairly common, and so long as its less than 10 years your pretty much guarunteed a full recovery. Eventually.
Hope this helps