Of course one way to get high scores and clear a level out quickly is to get the biggest possible chains, by getting the biggest possible links. Your best bet is to get a five candy link, which will create a devastating candy crunch ball. Those balls can be mixed with basically any other special candy block, and will cause devastation to the board.
Never losing life
In most games you'll get energy to use for each mission, but in Candy Crush Friends Saga, you can keep on playing as long as you don't fail. You get lives, and you'll regain them over time, and only lose them if you give up on a stage. Which, if you run out moves and don't want to use gold, will happen. It's a pretty good system, as long as you stay focused on your target and make smart decisions, you can keep playing for hours.
Stay on target
Each stage will have a specific target, usually relating to knocking out certain blocks. Focus on the goal ahead, and don't get distracted. Only candy linked right next to, or on top of the desired blocks will break it out, and any moves which are a distance away from the blocks will essentially be useless. You can use these moves to set up big links or combos of course, but keep in mind how many moves you have remaining.
The one for the job
You'll get more than one character to choose from in Candy Crush Friends Saga, and which mascot you pick will alter how the games play out. They each have a special ability, allowing access to item use, or perhaps they will turn certain blocks into special blocks. These small changes can greatly help you clear through certain levels, and luckily, the game will recommend which character it thinks is best for any given stage.