Links Crossbow Training

Hint: Scarecrows

While playing through some of the target practice levels in the game, you may see a Scarecrow. Shoot it in the chest as many times as you can when it appears, a minimum of eight times, and you will hear a bell chime. When this occurs, the head of the Scarecrow will get bigger. Shoot the head to get a quick 1,000 points.
Now, if you did this correctly, later on any given stage, a second Scarecrow will appear. Repeat the same process on this one as you did on the first one, shooting it at least eight times in the chest and then shooting its head. If you do this, when the screen changes for a third and final time on the stage you're on, a new level will appear instead of the normal third leg of the stage you're on. More points will be available here.

Hint: Platinum Medals

Platinum Medals seem nearly unobtainable in many stages throughout the game. The prime way to build up your points to "platinum levels" is to simply rack up large streaks of hits without missing. Otherwise, you will have considerable difficulty in getting Platinum Medals everywhere.

Hint: Tri-Force

Make sure to never miss a target while you're playing through a level. Not only will this build your own point total higher, but if you reach the end of the stage without missing, a 5,000 point Tri-Force will be presented to you.

Hint: Ignore the Zapper

This is a pretty obvious hint, but one worth stating nonetheless. While this game comes with the zapper peripheral, the game is much easier and more manageable by using the Wiimote and nunchuck as they are, without the peripheral. This is especially good to know if you're going for the extremely difficult Platinum Medals on each stage.

Hint: Orange Crystals

As you've already mentioned in another hint, there are extra points that can be acquired by breaking pots, barrels, skulls and the like. However, pay close attention as you break these objects, as sometimes Orange Crystals lurk within. These will reward you with extra points, in the range of 200-800 points per crystal.
Correction by Colin Moriarty: If you shoot a jar or other object and a gold coin comes out, shoot the gold coin immediately. They're worth 1,000 points if shot immediately, and as the coin floats down, it becomes worth less and less, until it's worth next-to-nothing.

Hint: Scarecrow Points

For a quick 3,000 points on any given level, hit any scarecrow ten consecutive times in the chest. Then, hit him once in the head. If done correctly, you'll net 3,000 points.

Hint: Medal Breakdown

Here's a score breakdown for the game. You can earn the medal listed by scoring the appropriate amount of points on any series of stages.
20,000 Points - Bronze Medal
40,000 Points - Silver Medal
60,000 Points - Gold Medal
80,000 Points - Platinum Medal

Hint: Shoot Doors

If you want to make some extra points, try shooting the doors on various buildings you encounter. When you do, balloons will appear which can be shot for 100 points a piece.