Has anyone tried to make their own Sudoku puzzle? How is it done, and do you need a computer or can you just bang one out by hand? Is there a trick to which numbers to keep on the puzzle as ‘starters’ and which not to? What about longer puzzles with more than 9 numbers… are they functionally any different or really any harder? 
Personally new to Sudoku - just now getting hooked with my wife on our morning bus/Metro commute… and it IS addictive.
(moved this myself from GQ)
Sorry I’m no help to your answer, but I share your curiosity.
I’ve wondered how they were constructed. I figure that maybe the author would -
1 - create an entire correct 81 number grid to start with
2 - erase the numbers backward using a reverse logic style (like saying to yourself, "I can erase this number because there are already other numbers showing that force this spot to be unique)
3 - Continue erasing numbers until the erasing of any of the remaining numbers causes the grid to no longer be unique.
4 - reinsert the numbers to build the grid to the level of difficulty desired.
I’m not saying this is how its done but its the only way I would think of trying if I were to build one.
Iv’e also wondered if some of the grids can be cheted by replacing all 2’s with 3’s and 3’s with 2’s to yield correct grids.
In any case, I’m a Sudoku addict. My favorite Sudoku online site is here
Its a java based engine with puzzles ranging from easy to insane.
If you haven’t been there give it a try.
I tried working a “longer” Sudoku from a book once. The size of course, increases from 3 to the third power (81 spaces) to 4 to the fourth power (256 spaces). I was able to do a few numbers but the mental logic of following 16 numbers instead of 9 wore me out pretty quick.
Like other Sudokus I imagine the 4 to the 4th could be set up as “easy” or “hard”. In the case of the one I was trying to do the grid was very busy with “given” numbers but still very difficult to logic my way through. I ended up setting it aside until I hopefully improve my skill level.