For this achievement, you need to complete two scoring lines simultaneously with a single drop. This is actually required to complete one of the challenges called "Double Trouble." Use the following strategy mentioned by IEvil IMonkey. Put pieces in the bottom left and bottom right corners first. Then try to have them both meet, in an upward, diagonal line, in the middle column. Place the top of that triangle last. Try not to ever place a chip that would allow the AI to place one in either of those diagonals you are trying to fill (right below the diagonal).
This achievement is also obtainable in 2-player local multiplayer mode. Use the same method as above.