First board: Focus on the narrow path in the first column AND on the tile of the exit. Whenever you get the opportunity to match some diamonds there and destroy those ground blocks, do it! Don't miss the chance. Also, focus on getting the water to the exit. Don't waste your moves. Gold-striped blocks don't help - they don't bring much points.
Second board: Gold-striped may help a bit, but just by the way. Don't waste any moves on destroying them. Instead, focus on matches that'll bring the water to the exit as soon as possible, so that you can proceed.
Third board: This board is complex due to purple blocks. You better not use your Color Burst here. If you can BY THE WAY destroy some bottom gold-striped blocks, that's good. They bring 2,000 points each. But still, don't focus on them! Focus on getting use of every opportunity to get to the exit. Narrow column between purple blocks is tough, as well as the bottom. You need to have some luck.
Fourth board: Treasure Room, but not that cool Treasure Room - there are three colors, target score pretty high, and you probably won't have many moves left. Use Color Burst immediately, so that you bring some big diamonds there. Make matches with most number of them. It's not that easy, but there are harder levels!