First, remind him of his manners and encourage him to dress professionally. Even if everyone else in the office seems to have a laidback attitude and attire, tell him that it's important to establish his reputation early.
Next, Forbes magazine recommends sticking to the job and exceeding expectations. It can be easy to get distracted at the water cooler while speaking to coworkers, especially for someone not used to working in a professional atmosphere. Remind your son to keep his eyes on the prize - award and recognition from his boss!
Finally, tell him to speak to a psychic for more insight into the situation if he's worried about fitting in at his new workplace. A tarot reading can let him know how his next few months of employment will fare.