Roll 3d6 and drop the lowest of the three numbers. Do this six times. You may assign the six numbers however you like to the six characteristics.
You automatically qualify for and advance in your first career path. After that, the rules as normal, with six careers as the upper limit (unless you roll a natural 12 on the advancement for your sixth career track, then you get a seventh career; keep doing this until you stop getting natural 12s on advancement rolls). 3-4 career tracks should provide a useful starting point. It’s very possible to train additional skills during play if you aren’t satisfied with what you rolled to begin with.
Each PC can improve up to two skills one level each by using the ‘connections’ feature (see pages 8 and 37 of the Traveller Main Rulebook).
This is a new system for all of us, and because we have only a few players, we’ll probably all make use of multiple characters, just to test things out (and because it seems like the Party wants to start a space British East India Company; big things like that aren’t run by 3-4 people). While I’d like to keep the PC cast as low as possible, I’ll be fairly lenient on players who find the character they rolled not up to the tasks of the moment and who desire to try something fresh.