Which format to use if I want to print?

[JohnnyL]

Hi all , I have a question.

I want to print my photographs. Before the idea of printing came to me , I mostly shot Jpeg Basic ( I use a Nikon D80 , other brands may call it something else) which has been great for me to upload onto Flickr and all that.

So now I'm wondering ,if I want to print as big as A3 size paper, should I shoot in RAW or some other format instead?

Also , I've been editing my photos in Photoshop Lightroom. After I'm done with the editing , I export files and I have to fill in the blanks like File Settings , Image Size , Pixels per inch..... What are these?

Thanks!