For this i would recommend following the live betting games on any casino, lets say you are betting on basket ball, Bulls vs Nuggets, and nuggets are the underdog, the casino pays x3.5 on them, so you place a $10 bet. Then start watching the game, and for a moment nuggets start winning the game by score, which will make the bulls the underdog now, so, the casino offers x3 on Bulls, on that point you place a $10 bet on them. That way if any of them win then you will make close to 33% profit. The only risk here is a draw. But it's hard to see that in basketball.