HT Games
One Section
Keep to one section of the blocks as long as you possibly can. This will force you to work with specific colors and shapes and thus eliminate an entire section of the board faster. Keeping to one section of the board will also familiarize you with the symbols and images in that section so you'll be on the lookout for their pairs constantly. At the same time, don't get stuck. Don't waste all your time searching for a particular image to no avail. If you get stuck, then it's time to move to other areas of the board.
Colors
Use the colors on the board; essentially they're there to help you. Set your sights on a particular image and scan the entire board for images with that exact color. This will allow you to work faster and find matching pairs quickly. Don't waste your time re-clicking on pairs that you think the game should eliminate. If the game doesn't eliminate them right away, just move on to a new image pair. Otherwise, you'll waste valuable time.
Thumbnail
Players often forget to use the thumbnail to their advantage. As you run your mouse over each block, a small image of the item pops up on the screen in a thumbnail on the lower left corner of your screen. This is incredibly useful when your mouse runs over blocks that are concealed or that you can't completely see. This allows you to work over the entire board as strategically as possible, creating pairs from blocks that are underneath other blocks or blocks partially covered by other blocks. Constantly check the thumbnail as you play the game.