Been out today to test my new camera, just a few pics I took not brilliant but still playing with the different settings, what would be the best generic setting, P,M,Sv etc

Hi, Just joined today and seen that I've just got my new Pentax K-r today I'm sure I will have some questions over the coming weeks and months, as well as my camera I also got the 18-55mm lens, Tamron 70-300mm lens and a Kenko 2x adaptor so I should be covered for most things at least at the moment, I also have a Pansonic G1 and was looking at getting a new lens but got all of the above for almost the same price as I would have paid for the lens so it looks like I will be getting shut of my G1.

One question I do have, on the 18-55mm lens hood there is a little part on it that says open and pulls out, what is this for?