In any event, whether on board ship or in an Away Team, you're always going to be complementing your player-character with a selection of Bridge Officers, who have their own slightly more limited advancement paths. On foot, these operate like AI party members in a single-player RPG. On board your ship, they contribute buffs and skills, effectively joining with your player-character to create a sort of all-class meta-character. You'll collect a lot of Bridge Officers and be able to swap them at will, so there's huge scope for configuration, and no avenue is ever really closed to you whatever career you choose - vintage Cryptic design.
You begin the game as a lowly Ensign, assuming command of your ship during a catastrophic Borg attack. By the time you've romped through the tutorial storyline, you'll be a Lieutenant and officially have your own Starship Command. From that point, you advance through the ranks of Lieutenant, Lieutenant Commander, Commander, Captain and Admiral, and each of these has 10 levels. You can only employ Bridge Officers below your own rank. When you gain a rank, you'll be awarded a new special ability and the access to new classes of ship but most of your skills you choose and balance yourself by spending skill points. You don't need to visit a trainer to do this - it's right there in the skills window - but you are required to spend those points to rank up.
Gaining ranks and new ship types is a powerful levelling motivator, and progress is flexible, but with almost none of the traditional RPG stat mainstays to use as a bearing - and the split in skills between Ship and Ground abilities - it's quite easy to feel lost in this unfamiliar system at first. Nevertheless, it's so flexible and progress is so constant that learning on the job doesn't feel too intimidating, and Cryptic seems to have struck a nice balance between pure skill- and level-based styles of progression.
After the tutorial you arrive at Earth's spaceport. It's a social, trading and customisation hub, a standard MMO town in other words, with vendors, mission givers, an auction house and a bar. Stations like this and "sector space" - which is basically an over-world map - are the only places in Star Trek Online that you'll actually see other players running or flying around unless you group with them (well, more or less - Cryptic has said that the star system instances aren't entirely locked and you may end up playing with one or two strangers, but I haven't observed this in the beta yet).
Accepting your first missions, you beam to your ship via a loading screen - bridges you can visit have been promised, but aren't in place yet - and then warp to the abstract map of sector space. Here you can fly manually, or via autopilot, to star systems. There are occasional roaming enemies, which trigger an instanced space combat mission if you fly too close, and also "fleet action" points where multiple groups of players can take part in large-scale player-versus-environment space combat.