Obi-wan finds Anakin as a mid-to-late-teenager
Anakin becomes Obi-wan's pupil, learns the way of the Jedi
Separatist coup on Queen Amidala's home planet
Separatists secede from Republic
Anakin and Obi-wan are sent on a rescue mission to save Queen Amidala (this is an opportunity to simultaneously develop the relationships of Anakin and Obi-wan, as well as Anakin and Padme)
Palpatine becomes Supreme Chancellor of Senate (or President, or whatever)
The machinations of the Clone Wars set in motion
That allows Episode II to actually be about the Clone Wars, and gives Anakin and Padme plausible time to fall in love and get married yada yada yada...
Not tied down to much except setting up Luke and Leia's birth via a marriage with royalty if you ask me.