Breaker Barracks Gold Medal
If you upgrade the bow to have +50% damage, the second bow upgrade, you can destroy the targets in one shot, without needing a power shot, making the gold medal much easier. If you are short on upgrade materials, getting a bronze medal will give you one something stringy upgrade material.
Bullhead Court Gold Medal
Although it says the requirement for a gold medal is 2 or fewer hits, you can actually be hit 3 times and still receive the gold medal.
New Game Plus Mode
Beat the game to unlock the New Game Plus mode. In this mode your experience level, weapons and upgrades carry over. Additionally, you can build your structures in any order in the New Game Plus.
Slinger Range Gold Medal
Having trouble with the Slinger Range Proving Ground? You can't get negative points, so shooting a little bit before the first target shows up can get you a few extra points that can make all the difference when going for a gold medal.
Stick With the Repeater (Crossbow)
The Repeater (Crossbow) you get near the beginning of the game is awesome once upgraded with homing shots that are quite helpful. Stick with it!