If you really research many so-called "experts," what you find is that the vast majority of them have no idea what the hell they're talking about. Once you get past the superficial stuff, they're no more capable than the average Joe off the street. What sets them apart is the aura of being an authority.
So, how do you make yourself an authority without actually going through the work of becoming a real expert? First off, learn the lingo. You have to sound sophisticated and in the know. You don't have to know what the words mean, but you need to understand what contexts they sounds correct in. Learn the fine art of technobabble b.s.
Next, invoke seniority and time in the field. Nothing makes you an expert faster than having spent time in a field, even if you learned nothing during that period. Spout off figures like "I've been doing XX for YY years, and this is how I know it's done." The more years you can say you've been doing something the more authoritative you'll be.
Lastly, assert yourself. Tell other people that they're wrong, and come up with reasons that you're right. Be forceful and adamant. If you seem to waiver in your convictions, you'll be perceived as a loud-mouth dunce. Act like an authority and strong leader, and people will perceive you as such.
In the off chance you do run into an actual expert and authority, not to worry. All you need to do is bring the other person down. Criticize anything possible that you can think of and attack their credibility. If you can't bring your perceived authority up, you merely need to bring everyone else's down.