Since writing my first tutorial it became clear I hadn't included enough detail so I have re-written it for more clear instructions. The first part goes into a lot more detail about the joining and as such its a good idea to read it through before the others.
The later tutorials do not include as much detail in places as the earlier ones. It is hoped that by the time you get to part 3 onwards that you can make joins from part 1 without the detailed explanation.
US Terminology throughout.
Part One - Joining Two Same Size Squares Together
In this picture we are adding the red square. There are less pictures than in earlier parts but you should hopefully have the hang if it by now :)
Granny Style Squares.
These are dealt with pretty much the same as the other joins, begin with the chain in the corner and join each stitch (or chain) to its opposite ending with a chain at the end. Its just in this case you are sometimes joining chains to chains and DC's to DC's.