The SWG website has published a very good article describing the expertise tree for commandos and explaining how the kill meter works.
Two classic examples of Commando expertise templates are also explained in details.

• Diagnostic Armor is very helpful in PvP as many players will try to use damage over time effects against you.

• Blast Resistance can reduce the area-of-effect attacks against you to zero damage. Most creatures and non-player characters do not use area-of-effect attacks, so it is not effective against them.

• Grenades are predictable in PvP and easy to avoid, so most Commandos use heavy weapons and plan their expertise around it.

• Remote Detonator is best used against non-player characters and creatures, although a group of commandos laying in wait on a battlefield near a choke point could easily take out an entire team of players with multiple detonators.