Since you don't mention Bloodlines or Redemption, i am guessing the latter. Feed also wastes much more xp to invest in and is inferior to other alternatives. Theft of Vitae is the best and most effective, plus cheap. Once or twice, it completely drains someone from blood. Vampires cannot use disciplines at all and are quick to frenzy, mortals die on spot but without yielding xp. You can also use Tongue of the asp or whatever is called, the setite discipline, but you get it much later, so it isn't really worth it. If you need blood though and have run out of "fuel", you can always use one of the many items (rat, pouch, pearl, stone, bottles, bloodpacks).

In bloodlines other than feed and the bloodpacks, there are no other alternatives.