I was reading thur some post and the guy was using SimpleGame and somebody replied you should make your own SimpleGame is no good. Then i noticed i'm using SimpleGame so i was wonding what are the steps in making your own game type.
Give me another hour or two, I'm in the middle of writing this very tutorial. And you can be the first editor, letting me know where it sucks. 
Ok, http://www.jmonkeyengine.com/wiki/doku.php?id=flag_rush_tutorial_series_by_mojomonkey
second tutorial.
I somewhat rushed it (it was kind of boring to write ), so I'm sure there are plenty of mistakes. Please let me know.
Also, SimpleGame IS good when you're trying things out or have a quick visualization to perform. If you want a full blown game though, roll your own as the tutorial demonstrates.
What I did was I copied the content of the SimpleGame class to a new one and changed bits and pieces. I started my game client with a class extending SimpleGame and I just changed it to extend the copied class instead. That way I had something working and could explore the things that SimpleGame did for me.
After the first "exploring phase" I cleaned up as I had some redundancy in the first class and the copied SimpleGame.
Well, my first time to "break away" from SimpleGame I opened the source code for SimpleGame and created a new Class and went line by line determining what everything did and ignored the majority of stuff in it because a real game really doesn't need most of the stuff in there and does need other stuff. I noticed that everything ran significantly faster after I had made the move.
I would suggest something like this above just copying SimpleGame over since it adds a lot of overhead to your game.
darkfrog
or you could read the tutorial. 
renanse++
nice tutorial very impressive and detailed