I was reading through the topics and didn't see this mentioned in any I think... well something to keep in mind for any profession that has a skill related responsibility.
Make sure you don't have those skills maxed or you might find it is slower to get promotions (because maxed skill seems to mean no more experience gain, no matter how hard you work out, tinker etc.).
Also the whole Co-workers thing with professions seems to have no impact on experience gain (at least I noticed no visible progress on the bar, while socializing nor when relationship status changes... maybe good relations net you bigger boost when doing the "main" responsibility, like handling emergencies for firefighters, I don't know).