Some more ideas:

When Ben meets Luke first, change the dialoge from "I don't remember ever owning a droid." to "Obi-Wan remembers owning R20000."
When Luke wants to persuade Han to rescue the princess make them say:

Luke: They are going to kill her!

Han: Better me than her.

And then they just leave. Maybe swith around some more dialoge to make it look as if Han wants to go and Luke doesn't.

Han: Marching into the detention area is what I had in mind.

Whenever Luke hits someone with his Blaster, Han says: "Great shot, kid. That was one in a million."