If I buy a new Apple computer how do I transfer all my documents and pictures to the new computer?
With Migration Assistant. These are the Mac instructions. You can also migrate docs from a PC.
Don't use Migration assistant. Just copy all those files to an external hard drive then move that drive to the new Mac and copy them off it to the mac.
If the current computer is a Mac, you might consider Target Disk mode:
This eliminates the unnecessary extra step of moving data twice.
Retrieving data ...