There is a very good tutorial from B+H here
It is for Lightroon 5 but the principles would be similar even if all the features are not in your version.
I think the key is to get your file structure on your computer organised in a way that suits you before your import anything. Some folks organise their images on subject matter like travel, nature etc. Others prefer a date based structure, wedding photographers may prefer a client based structure. It all depends on your preferences. Get it right and the catalogue is a blessing. Get it wrong and you will curse it forever. If you can recall where you were on Jan 15th 2010 and what your were photographing then a date based system may be for you. If like me you more easily recall subject matter, organise your hard drive that way that way
eg:
C/Images/Nature/Flowers/Melton Botanical Gardens 2016-06-11
Note: Local to me so I go there a lot so the date is relevent
C/Images/Events/Fred's Birthday 2014-05-01
Note: Unique event and the date is important but I am more likely to want to locate an image of Fred
C/Images/Travel/Australia/Queensland/Bundaberg 2015-08
Note: I travel to Bundaberg often, so year and month is relevant
C/Images/Travel/Overseas/China 2013
Note: I go there once in a lifetime so year is relevant but exact date not so.
Adding key words may be laborious if you have a lot of photos but well worth the time
Once you import your existing images using the ADD command it is time to import from the camera using the COPY command. For this I have a folder called "AAAA New imports" so it is always at the top of the tree and import all files from camera to there using Copy command. As previous response you still have duplicate on your camera card. From there I sort into sub folders eg. Johns Birthday 2016-o9-01 and move the subfolders to the appropriate part of the file structure so they become a subfolder under Events. While still in the subfolder it is a good time to add universal keywords to the files in the folder. eg "Birthday" "Fred" "People" "Events" and so forth.
Now the REAL IMPORTANT thing is to never use the computer file system to move files, copy, delete or rename them. They they will be lost to the lightroom catalogue. All these functions should be done using the Lightroom file management tools. It is possible to recover things but you can create a real mess.
RAW: PEF v DNG is personal preference. I use PEF as when I started I was not aware of DNG and see no real reason to change now.
Always backup your catalogue regularly but remember this does not backup your files.
Good luck.