In the final stage of 7-3, hit the ropes above the red ruby...it sends off explosives and opens the gate to the scarecrow. It allows big points!
Alternate third area
Shoot the scarecrows that appear from time to time on a target shooting level. After hitting its body eight times, its head will swell. Shoot its head for 1,000 points. If you shoot the heads of two scarecrows in the same level an alternate third area will more gold targets will appear.
Explosive Arrow
On any level, hold the B button for about 4/5 seconds. The cursor should change colour. Let go to fire, wait a few seconds and bang an explosive arrow!
Extra points
There is a level with birds carrying targets. You are told not to shoot the birds. When you shoot them, they will drop the target. If you shoot a falling target, you will get more points than if you did not shoot the bird.
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.
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
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.
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.
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.
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.
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.
Shoot Doors
When you shoot the doors on the various buildings you encounter balloons will appear which can then be shot for 100 points each.
Shoot Zombie Heads
At the end of stage 7-1 when zombies come at you, shoot their heads to kill them instantly and get 20pts per head.
Super shot
When you hold down the B button you do a super shot.
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.