I like SAGA. It plays well out of the box. I also include a "Skill Training" type feat in my houserules. That's the only firm houserule I use. I do point out a couple of potentially broken things involving manipulating the condition track, and ask my players not to do that :-D.
Pretty generally, I try to find out what sort of character someone is really interested in playing. This is easy with anyone who's read into the Expanded Universe, as it's such a character-rich setting that they can say they want to be "like Corran Horn" or "like Gavin Darklighter" or "like Talon Karrde" and I'll know what they mean, then with a few questions can zero in on their perception of that character. I then help them fit into the system, or I fit the system to them. One guy wanted to be a 'pile o' armor' marine type, so I altered things to where it was actually a (minor) advantage to do so even though the basic game favors those in Light or no armor at all.
Basically, it comes down to make sure your players have fun.