How do you think they start? From scratch, learning from books or from others, or in school, or college. There are lots of ways to do this, I am sure you can even find tutorials on the net to get you started, but don't expect it to be easy. As for a Sierra games emulator, if S60 phones and the N-gage can do it, the PSP definitely can. So it's only a question of time, not of whether it can be done.