Check the Tiles
By holding down the "CTRL" key and the left "Shift" key simultaneously, you are able to see what the board looks like without the jewels on it. This allows you to clearly see which tiles are gold and which still need to be converted to gold.
Clear Locked Squares First
The only way to unlock a locked square is to match up coins. Try to match all the coins on the board at the beginning of the level and then move on to matching the jewels.
Work from the Bottom Up
By trying to make lines of jewels that are closer to the bottom rather than the top, you will be able to make bigger chain reactions, allowing you to complete the level faster.
Use T- and L-Shaped Patterns
Survey the board and look for areas where you can swap a jewel to make a T or L shape of identical jewels. If you can do this, you will get 4 or 5 points just for moving a single jewel.
Keep an Eye on Your Score
If you can see that you are approaching the point goal for the level, you can take your time and look for the best moves to make.
Plan Ahead
Make a note of where jewels are on the board. If you've got time you can make the appropriate lines so that identical jewels will fall into place next to each other and set you up for a chain reaction.