Just some tips i pulled from the guide I made on x360a:
This achievement is for beating all 100 levels
-Learn to combo your combos This is the best tip I have, combining 3 line clears is nice, clearing 2 lines thick in 3 directions, especially for levels that have hexes in areas that cannot be gotten through normal combining. Even better however is combining a color clear with two line clears, it turns every hex of that color to a line clear, and immediately fires them. Learning to do this well is really all you need to finish this game.
-Most levels are not timed, no need to act like they are, go ahead and think about more than the current move to make a juicy combo.
-The anomaly drop levels drop the anomalies on specific turns, but its still important to get the earlier anomalies down fast, if you get two or more near the bottom it gets really hard
-On anomaly levels with multiple obvious paths, try to clear one path and, if possible, exclusively clear hexes on that path so the anomalies drop onto it
-On dark frag levels clear bottom first, specifically bottom corners, the top may largely clear itself
-When on tricky dark frag levels make note of where you were having trouble clearing and clear it first
-Timed levels are usually pretty easy to beat, but hard to 3 star, at least for me, so I tried to steer clear of them for The Number achievement