Recently received a job offer, how to bring up negotiations?

Recently interviewed for a position, the interview went quite well and I was offered the job about two hours later through email. We did not discuss the offer at all in person. The only mention of money in the interview was when I vaguely mentioned what the recruiter told me the pay was (over the phone) and asked if that was negotiable, to which they said it was but said nothing else.

So now I have the offer, and it feels a bit low, I did some research and the information says that the number they gave me is certainly in the ballpark however I don't think it would be at all unreasonable to ask for a bit more.

My question is how do I go about entering the negotiation discussion. I received the offer from someone that I met for about 2 seconds and didn't interview with at all. They are a fairly large company and I'm fairly certain the people I did interview with aren't in control of the salary negotiations. The offer said if I have any questions please call or email. So should I just do that, give them a ring ask some questions and then say something like "I want to talk about the salary."