How to insert at the end of the line

Info

When I navigate with arrow keys or h,j,k,l to the end of the line and press i to enter the insert mode, it always inserts just before the last character of the line and I have to always press the right arrow key to start typing. Apparently it is not the best way.

What is the correct way?
What if you want to insert / append at the end of a file?

In this case, in normal mode, you have to first press G (capital G) and o (small letter o).