How to properly place your DSLR camera into a camera case/bag?

I got a nikon d90 and a lowerpro adventura 170 as a bag to put it in. How do I put it in? Lens down? Screen down? I don't really know.

Definitely screen down with lens up!

I'd put it in so that it's easy to get out quick to shoot. For most shoulder bags that's lens down.

In my opinion, dSLRs shouldn't go into bags. You might miss some pretty cool things to shoot if you still have to fiddle with the zipper.

Depending on the bag (obviously I'm not familiar with any), you can put your camera any which way you are comfortable with. Some bags don't give you much of a choice having shaped to have the camera face lens down for easy retrieval and hands-on position at once. With others, you really just have to use common sense. What is important is the camera sits comfortably in the bag without anything poking through the lens or any of the LCDs.