Hello, I recently made a character with the intention of him joining the Vampires should Dawnguard ever come out on PS3. Anyways, I know that as a Vampire you should have the Necromage Perk. But How do I play as a Vampire? Any tips would be greatly appreciated.

You have to avoid stage 4 hostility. There's two ways of doing that - one difficult and one easy. The difficult way is by Sneak and Illusion, the easy way is to feed. It's up to you then how you go about fitting that in with what you want to do with your vampire.

I was playing a vampire quite a while before DG was announced, and I played him as a serial killer and cannibal. He would lure unsuspecting people into following him to their death. I didn't do the MQ or any guilds, but there is still a lot of gameplay to be had with just the followers' favour quests. Here's a couple of videos from way back:

http://www.youtube.com/watch?v=Y68Y4-stbtY

http://www.youtube.com/watch?v=m7tRbcxl6w0

Play how you want to play bro. For example, vampires in skyrim hate fire. My vampire on the other doesn't give a shyt about a little fire and is a fire mage. That's the best quality of this game, do whatever you want.

I loved playing as a Vampire before Dawnguard. I had a routine where I fed every day on my follower (whom I RPed as being consenting, since I wanted to play a morally 'good' character). Owning every house helps for this as you have to ask your follower to sleep in a bed that you own.
I enchanted myself some gear with Fire Resistance, and Regen Magicka, Regen Health and Regen Stamina for going out in daylight. I took Necromage rather late in my game, but still benefited quite a lot from it, and another perk I'd recommend is Quiet Casting. With this perk you can more easily go invis in any situation where you feel at risk and as a Vampire you get a nice bonus to Illusion and Sneaking. I also got the spell Pacify to calm NPCs in case of stage 4 'accidents', as I cannot stand losing any Named NPCs. You can purchase it from Drevis in the College of Winterhold. As a lvl 81 Necromage Vampire with 100 Illusion I can calm most (I think all normally friendly NPCs, but not all enemies) of the NPCs in Skyrim and run away if I have to.

I miss having to keep track of the time and day now feeding is not essential to avoid hostility. Having to manage vampirism made me more aware of in game things like day and night, risks of fast traveling, the time, and how many days since I last fed. These aspects also didn't seem restrictive to the point where any kind of play style would have been compromised - and really as a Vampire you have just as many, if not more, options of playstyle, since as a vampire you can be one of the most powerful PCs that the game allows.