Now, I'm aware of the method of trapping a vampire in a room with spikes and repeatedly impaling them with spikes is a common method of getting the pool of vampire blood you need to infect your fort, but, there is an easier solution that I just found!
Step 1: Make a 1x1 well in your fort that goes at least 3 levels deep. Have a back wall to it - this will be important later
Step 2: Continually make adventurers and topple statues in temples until you're cursed with vampirism (check legends mode on your character to check using open-legends in DFhack, or by retiring & unretiring your adventurer)
Step 3: This is the hard part. Acquire mugs & goblets, and then make yourself bleed heavily onto the ground until you have a pool of blood on the floor. Then, without dying, scoop up this blood in the goblets and mugs you've acquired and head to your retired fort. (I achieved this by repeatedly jumping off of high ledges and healing myself promptly after in DFhack)
Step 4: This is where that wall behind the well comes in. Throw the goblets & mugs with the blood in them at the wall so that they fall into the well. If you've done it right, there will only be one 7/7 source of water at the bottom. with a few mugs & goblets of blood in them
Step 5: Unretire the fort. There will now be pools of blood in the bottom of the well with the goblets there as well, as the goblets automatically spill their contents upon unretiring.
Step 6: Forbid all alcohol and water sources, set drinking to zone-only, and profit! You now have a means of getting a vampire fort.
That's it. Should be easier than the method Kruggsmash used and it works - I've just tried it and I have a well with a pool of vampire blood in it. Good luck and happy bloodsucking!
(My goblins are modded so that they dont have [NODRINK] specifically for this)