Anything goes in Normal mode, by which we mean that all you have to worry about is clearing as many blobs as you can, as quickly as possible. It goes without saying that you need to make sure the highest color blob doesn't pass the top of the cylinder.
High score Timed mode
This mode's much trickier than Normal, as you're playing against a ticking clock - and once that timer runs down it's game over. To top up your time, you're going to need to clear out those blocks that have a clock icon inside them. This gives you more time to keep playing, so you should always prioritize clearing these out when you see them.
If you're struggling to get much of a high score in the Timed mode, you might want to think about spending some coins on this Perk. Activate this and you'll get a little more time to play with.
These are great for destroying a large number of nearby blobs, making the game area easier to work with.
Various Game Hints
Increasing your rank in Rise of the Blobs opens up new themed stages for you to play on. If you want to increase your rank, keep playing and chasing a higher score, as each match will reward you with experience which fills up the rank meter.
Rainbow fruits will occasionally spawn on the game board, and are capable of absorbing fruits of any colors. Handy if you want to keep your game going longer.
TNT Blobs are great for destroying a large number of nearby blobs, making the game area easier to work with.
If you're struggling to get much of a high score in the Timed mode, you might want to think about spending some coins on Time Bonus.
Cherry Bonus will add a bonus to your score, based on a percentage of your total score.