Jango Fett got his start as a
farmboy on the planet
Concord Dawn (which also happened to be the homeplanet of the leader of the
Mandalorian Warriors).
The Mandalorians were in a battle with an off shoot of their group named the Death Watch. These two groups are battling on Concord Dawn when the Death Watch murders Fett´s family.
The young boy gets his revenge by helping the Mandalorians wipe out the Death Watch. Jango now an orphan joins the Mandalorians on his way to becoming the best bounty hunter in the galaxy.
At some point about 10 years before Episode II, Jango is given the honor of becoming the template for the Clone Troopers, after being selected by Count Dooku.
His life is ended by Jedi Master Mace Windu on the planet Genosis leaving his clone son Boba Fett to carry on in his footsteps.