Finding someone to play online these days is half the battle. Boosting with a friend is an option, however if you go for this legit then here are a few tips.
CRUCIAL POINT: Every three correct answers provides you with a bonus "card" which you can use to swap with one of your existing cards. You should swap it with your EXISTING BONUS card as this will maximize your potential score. You earn no points when playing a bonus card. Answering the brain challenges is the key to earning points. If you find a n00b who swaps the bonus for a question card you will beat them every time providing you answer all your questions correctly even if done slowly. Swapping for a question card has cost them around 200-300 points.
Balance going for the online achievement with your offline progress so you are getting some practice and can perform well online.
Play at a skill level you are comfortable with.
Update: Just adding that some people have had issues with this unlocking at 100 wins and had to play a few more games to unlock. WraithTDK in the other solution required 111 wins.
Personally I got mine bang on 100 wins but if you don't, keep playing a few more.