What are your suggestions in taking pictures in a coference?

Its an indoor conference, lighting would be probably dim. I have a nikon d90, I just got my camera and still in the process of learning. Feel free to share your knowledge and tips.

AA-RG! What is this! An old and retired film photographer giving a digital camera user advice?

Conferences are interesting places.
Before conference starts, mingle and tell enough people the type of pics you are expecting to take or have someone inform participants. That way the pics you take will not end up looking like some sort of goofy personal pics.

Before conference starts, like as early as you can, find out from organizers purpose of conference, list of important events and speakers, and participants.

Be pleasant. Be unobtrusive. Move about quietly, yet purposefully. Try to not be the focus of attention. The people there are the true focus of attention. Photograph anyone and anything that catches your eye. Photograph important moments. Speakers. Objects.
Write names of people to match photos of said person with pic and information for use as photo captions/stories.

Sorry I can't give you advice on how to use your digital camera… Old film guy myself, you know.
Good luck always sounds like who ever I'm saying it to is to be fed to wolves…
Sending you off with what an instructor and several bosses told me is more appropriate…
Get to work. Find out what is going on at the conference in advance and get some photo, and story ideas. Get your gear… Now get outta here… Not paying you to stand around!

As you say, the lighting is going to be dim so unless you are going to bring some strobes in, you know the problem you'll have. The first step would be to boost the ISO as high as you can before your images develop too much noise. I don't use the D90 so I can't give you a clue on this but maybe others can.

I would bring your fastest glass (largest aperture) so that you can capture as much light as you can.

If you are planning on stopping down to increase the depth of field, have a tripod or, if a tripod would be too obtusive, a monopod or some other way of steadying the camera as you'll be having some relatively long shutter lengths. Be sure your vibration dampening is turned on if you are hand-holding.

First and most important.

Flash will be a bad idea: It would make the picture just look too bright or too ugly if you are focusing on a photo.
But if you have to use flash, then use it wisely.

Some tips about flash:
-Do NOT Focus on objects, or get too close, or too far.
-Angles would be good to use, if you want to make it as an overhead, the flash would work. Because you would be the top and the flash is lighting everything in range.

Now other tips you may need are:
-Taking your time in the photo: You will need to take your time, to make it look perfect, or just at least impressive. But if you are looking for taking 300 pictures and then deleting the pictures that aren't good, then its your choice.
-Don't take too much of the same picture: This would make it boring and simple, go for different parts of the room, as said above, make it an overhead, or kneel down, then zoom in, and it would look as if "a sniper scope" as I like to say.

-Modes: I'm not sure if Nikon D90 has modes, but if it does look for close up mode, or auto mode, or scenery modes, or sports mode.

Close up mode: If you are closing up on some ones face or an object.

Auto: It would do everything for you, I personally favor Auto because it does everything for you, the blurs and sharpness etc.

Scenery: This wouldn't be best, but it still is good, its used for a view of everything, its simple enough.

Sports: If someone is moving fast, or a lot of things are happening at once, sports would be best. It takes the images fast, and sharp, but sadly limited freedom with blurs and sharps.

Hope that helped!