Ok, I've seen "spells to become a vampire" on my little search reports, so there are more than a few people who are looking for this sort of magick, which really surprised me. You seriously want to become a vampire? Well, I'll at least give it a mention.
This kind of magick falls into the same category as the spells for eye color change, which is to say that it's not real. It's movie magic at best.
In my opinion, vampires are mythological beings that do not exist. But I will grant that I am not a complete expert on the entire universe and could possibly be wrong. So in the odd chance that they do exist, the lore is that you don't use spells to become a vampire, you can only become one if you are bitten (and survive) or/and if you drink their blood.
Different tales provide different ideas for this, but you can't simply make yourself into one. It doesn't work that way. So I really have no spells that I can offer you that would even come close to turning you into a vampire.
My last thought is, why would you want to be one? I suppose the idea of living forever might be appealing, but being driven to kill and drink the blood of others is hardly a pleasant way to live. Perhaps you're enamoured with the idea after seeing the Twilight movies. I sure hope not....
If you're just looking to get in touch with your darker nature, there are other ways to do this. I don't have a lot of black magick material on the site, but you can explore the realms of bindings and banishings to start with (update: I do have a new black magic section!)
So, sorry I cannot help any more than this for any spells to become a vampire. I wish you luck on your journey though. If you do find any spells that work, feel free to let me know.
Prefer another mythological being? I have a page for mermaids too.