How do you be a dick?

That just means to be rude or a jerk. That is something to strive not to be. Here are some of the behaviors and qualities associated with such persons:

• Belches
• Bigoted
• Complains a lot
• Expels intestinal gas
• Expresses politically incorrect views
• Inconsiderate
• Intoxicated
• Pulls out in front of others in traffic
• Rude

Now if you mean a detective, then you would have to go to school for that, and possibly police academy if you mean a police detective.