So, I haven't played Skyrim since I got my new PC parts and changed shitty harddrives and as such, all my save games are gone. How do you know when and where Dawnguard starts, I'm level 5, people know I'm Dovahkin, where do I go to start the DG stuff?
Well I got on a level 17 character of mine, and the quest started when I walked by a guard in Whiterun and they said something like "Oh man these vampire attacks are getting worst, we need the Dawnguard." and then the text appeared on screen and the quest in my log.
P.S. If anyone is thinking of starting a new character for Dawnguard, I highly recommend
Alternate Start - Live Another Life.
Instead of starting the normal way, it starts you in a random room with a statue. The statue lets you choose either the original opening or a large amount of new starts. Some examples I have tried...
A soldier in the army - you get to choose either Stormcloak or Empire, and it will load you directly into the factions main city next to the commanders.
A new member of a faction - puts you right into the faction of choice open to the starting quests, Companions, College, Thieves, or Brotherhood were the main options.
An owner of property in the holds - lets you choose any of the player houses or a random farm, so you start with the house of your choice and can adventure from there. Choosing the farm does not displace the people living there, but you can sleep there anytime and the farmer even gives you money from his profits.
A vampire hiding in his lair - starts you as a vampire waking in a small vampire hideout as the sun is going down outside.
A few other options are simple ones, like you just landed on one of the city docks to start a new life, were camping out near Helgen when Alduin attacks it, or are just a random guy traveling from tavern to tavern. You could be a guy in a shipwreck, a guy left for dead after a giant attack, etc... I even noticed a special one if you play an orc, that allows you to start as a member of one of the orc strongholds.
They also have some for special factions, like new Stendarr recruit, a Necromancer, or even a outlaw at a bandit camp that has decided your group is not getting you enough money. All of them tie into Helgen and have you go there, which allows you to start the main questline anytime. It's really well done.