What exactly an intel officer does varies widely based on who you are supporting and where you are assigned, but there are a few constants:
-Powerpoint: Be it, know it, live it.
-Take large volumes of information and distill it down to the essentials: Most of your job is reading, reading, and more reading, followed by summarizing (usually in Powerpoint). 99% of the time this is behind a desk, so find a good chair - and practice good ergonomics! (Carpal tunnel sucks.)
-Feed the Beast: In this case, with paper - you do a lot of report writing. In a squadron, you're the one writing the MISREPs (mission reports). (And believe it or not, these actually get read, so make sure you don't blow this off.) In a shore environment, you are usually analyzing a particular narrow topic or geographic area, and then writing about it; sometimes daily, sometimes weekly, sometimes at longer intervals. You will be a "go to" guy concerning that topic. Which leads to
-Know your stuff: Can't emphasize this one enough. You're only as good as what you know, or more likely, what you can find out. Your role is an information provider, and if the people asking the questions think you don't know what you are talking about, they will discount what you say or ignore you entirely. Work hard to become a subject matter expert (SME) concerning an aspect of your work/community. Important caveat: Only give answers you are sure of - never guess! It's always better to say "Not sure - I'll find out" than to have to hunt someone down and retract something. In a squadron, do everything you can to get smart on your platform's mission, concerns, and issues - you need to be able to "talk the talk" to the ready room, even if you can't "walk the walk".
-Never stop learning: Correlates to the above. It's really easy in this line of work to become obsolescent quickly. Knowing the pre-OIF Iraqi AOB and DMOB isn't helping me a lot career-wise these days...
-Have a thick skin: Especially in a ready room environment, where no quarter is asked and none given. As the most junior O in the squadron, you'll take your share of HEAT rounds. It also helps to minimize the buffoonery on your part....
-Don't be a shrinking violet: This correlates with the thick skin advice; the intel field is full of introverts to begin with; you can really break out of the pack if you have an outgoing personality.
-Take care of your troops: As a div-O, you will likely have at least a few IS's working for you. Make sure you are looking out for them personally and professionally. They can make you look like a hero or a goat - which one can be very dependent on how they are treated by you.
There's more general advice in this message than "what do you do", but these things tend to be closely coupled...