This doesn't require you anything extra, just your regular BTC deposit at MetaWin and take the chance to win 0.20 BTC.
The tweet suggests you must repost + follow in addition to the
BTC0.002 deposit. How will they match users' Twitter and Metawin accounts though?
It can be done through cross check. Like picking the winners from repost and then checking if they have deposited. Or picking users who are eligible by deposit and then asking their twitter handle.
For this competition in bitcointalk, I wont check twitter either.