1. Captain Jean-Luc Picard
2. Commander William Riker
3. Lt. Commander Data
4. Lt. Commander Geordi La Forge
5. Lt. Worf (Security Division)
6. (Ships Services)
7. (Ships Defense)
8. (Sciences)
9. Commander Dr. Beverly Crusher (CMO)
10 Lt Commander Deanna Troi (Medical)
In the case of the episode "Disaster" Troi assumed command based on the fact that she was the ranking officer on the Bridge and because the lieutenant in nominal command was killed. Troi would not have assumed command had the lieutenant lived. According to another section in the guide, all officers at or above the level of lieutenant are assumed to have had access to certain areas of training and can be assumed to have certain skills:
1. pilot shuttle
2. fire phaser
3. operate tricorder
4. fight
5. operate computer
6. operate transporter
7. set a course
In addition each character has skills related specifically to their culture or job (i.e. Worf's exotic weapons, Deanna's prescribing psychiatric drugs), etc.