Some good pointers already!
The first thing that I would add is that, in my experience your CV has got you the interview, so the employer knows from that that you have the experience that they are looking for, so the main objective of the meeting is to see have you will fit in with thier existing team, and if applicable, would they be happy to put you in front of clients.
If the interviewer will be your line manager, he or she will be looking for someone they feel they could work with so in these respects it is important that you give the right impression.
Remind yourself that they are probably as nervious as you are, if I can, I try to make the interview a two way process, so that it becomes a conversation rather than a set of Q & A, this makes the whole process much more relaxed for both sides.
As said before you need to be able to demonstrate your strengths and see any weaknesses as points for development. I do think it is important to know your weaknesses, if you say you haven't got any, this will come across as over confidence.
If as you suggest, you tend to worry about awkward gaps in the conversation, a good trick is to ask for a glass of water at the start of the interview, you can use it as a prop. If you are asked a difficult question, you can take a sip of water to give you thinking time, just don't spill it!
As as previously stated, do some research, when you get to ask questions a good one is to start with "I see from your website that the company has just secured the ???? contact,...."
All the usual advice applies:
Dress appropriately, in something you are comfortable in, clean your shoes.
Firm handshake
Eye Contact
Arrive well in time (check your route beforehand)
Ant the end of the interview thank them for seeing you and ask what the next stage is.
NEVER ASK ABOUT MONEY AT THE FIRST INTERVIEW, let the interviewer bring up the subject, it they don't they are probably looking to discuss the package during a second interview.
Best of luck and try to enjoy it!
HH