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Finally got around to joining the companions and becoming a werewolf. Which is a lot better than being a vampire, only problem is you can't revert back to human form whenever you want to. And you have to reequip your armor each time you revert back.
That's why you go to Falkreath and talk to Sinding, ultimately doing the quest to recieve the Ring of Hircine.
If you get the ring before you become a werewolf, however, I do believe the number of times you can transform is unlimited. If you recieve the ring afterwards, I believe it is only once a day like any other power due to a glitch. But, the transformation is at will and you will not be transformed automatically.
As for vampirism, it depends. If you have the Dawnguard dlc, simply play along those lines and it will become available (even if you choose to side with the Dawnguard, you can still become a vampire through the quests.)
If you don't have it, just keep fighting vampires until you contract the disease, and then do not use any alters or cure disease potions until you become a vampire.