Re: Doctoral Programs
I just received my PhD in December and I work in a History Dept now even though I'm a geographer. It's been a long time since I had to apply but I know there are some simple things that you MUST do.
My overall advice is to find a professor at the institutions you are scouting and start to form a relationship. The more that you convince that person that you are serious and have an idea of what you want to do then you have a better shot. You'll need this person to be your advocate on the admissions committee, and you want to stand out amongst other applicants. It is very important to give them a strong sense of what you will do, even if what you actually do changes once you are in the program. So, you'll need to have a strong statement of purpose when you apply.
I would also take this time to interview them, to make sure that they offer an environment that will support you and facilitate what you want to do.
Personally, just playing Devil's Advocate here, I would question why you want to do a history PhD. History is a notoriously saturated field. Tenure-track positions yield a ton of applications (each position with 100+, so a TON of competition). New PhD's unless you are some sort of superstar, can expect to adjunct for many years on end with low pay and no benefits. I don't say this to discourage, but to inform. You really need to be committed to make it work with a history degree. These are things you might want to talk about as well with the professors you contact.
As for the mid-year enrollment, it does happen from time to time, so it's not out of the question. I've seen it before.
Good Luck in any case. PM me if you need anything.