First Move
Take your time with the first move. What you want to be looking for is the chance to acquire a power gem. You get a power gem by matching 4 or more gems in one move. You know it is a power gem when the gem has a significant glow to it. Once you have the power gem, you can match it just like the other gems. However, the power gem explodes when matched and takes out all the gems in its vicinity.
Play The Bottom
When you play the bottom of the screen, it is much more likely to create a cascade. A cascade is when the gems match and clear by themselves. Playing the bottom of the screen allows for more old and new gems to move in the columns and gives you a better chance to earn a cascade.
Alternate Sides
By alternating sides of the screen you can maximize time. Once you match the gems on one side of the screen, quickly look to the other side and make a match if possible. This way you are not wasting your time by looking at the gems falling and waiting for something to happen.
Play the Same Gems
Pick a gem and a try and play all of those gems throughout the board. If you get rid of all the green gems, the game will give you new ones in groups. Creating these groups with multiple colors will make the game play much easier.