What do you have to know before buying my DSLR?

I'm thinking of buying my first DSLR and I have decided on the Nikon D3100. What are some things that I have to know before buying one? Should I buy from stores that offer freebies like tripods, camera bags or memory cards?

You should know that a camera is only as good as its lens. Finding the best price may include freebies which are good, only if you need them. You may want to look at deals that get you the camera body but upgrade to an excellent lens that will best support the types of images you most photograph.

The freebies are up to you- just remember that you get what you pay for and you might be disappointed with the free stuff, anyway, and need to replace it soon. I would purchase a kit with a kit lens, though, as it's a decent basic lens that you will be happy with.

If you want to know how to use it to the best of it's abilities right off the bat then I would suggest to start learning what ISO, aperture, and exposure are and how they are all connected. That way, when you get your D3100, you will already be able to put it on the priority settings and manual setting. Make sure to read the manual that comes with the D3100, too, as it will give you a refresher on the settings and also show you how to change them on your camera.

Also, it's not necessary right now, but if you want you can take a look at how you photograph and what lenses you will probably need in the long run, and then maybe something like an external flash, etc. Then you can make a list and order it from most to least importance. Then, when you're ready to add on to your gear, you already know what to get.