To TS: First thing: don't rush. If you try to be as fast as possible you'll increase the chance of dropping something. Then, a good bag helps. I have a slingshot bag. When it is in front of me it's like a small table with an opening where I can access my lenses.
The rest is quite similar to what others have described. In addition: use lens hoods. After unmounting from the camera you can just put the lens front element down into the bag.