Can I select what unit I serve in?

Yes, provided that the unit has a position which aligns with your rank and qualifications. Unlike Active Duty, there are not mandatory unit transfers, you can seek out a unit and position that will be best for you personally and professionally. However, if the unit does not have a position for you or you are promoted to a rank higher than the position you are slotted in, it might become necessary for you to transfer to a different unit. At this time there are many empty 38G slots; Commanders are accepting most Officers who want to come to their unit.