Here's an important one:
Don't overuse "pace up" and "overtake". Instead of thinking of "pace up" and "pace down" as "speed up" and "slow down", think of them as "drive harder" and "calm down"
Let your driver negotiate other cars by himself, only use the overtake command on late-braking corners, that's where it'll make the most difference.
Bobs are useless at the beginning, and it can be pretty frustrating, but the rewards of having 6 B-spec drivers online to remote race with your friends is a great community effort that yields constant rewards.
Also, power is the best way to make your Bob win. If you're looking to win a difficult race, pump more power into the car, if that doesn't work, add even more power, if that still doesn't work, reduce weight and add power.
EDIT: And if you need cars to get through a Bspec race check your friend's online garages, or just friend and PM me and I'll be happy to put whichever ones you need up.