a) Follow Maverick's orders
b) Assertiveness is about *honesty*. Practice saying what you think, want, believe once a day using "I" statements. Ex.: "I don't agree with your idea", "I think I'm awesome, to be honest", "I think the PC market offers a palette of entertainment that is more mature than that of console games, considering the complexity of products and average age of gamers", "Excuse me sir, I was before you in the line". Oh, and insulting/annoying people is not assertiveness, it's being lame. Assertive people don't need anyone - annoying someone is a sign of need.
c) Eliminate the beliefs you have about people's responses if you are assertive. Some people will like you, others won't. The important is that you get to be authentic!