1.Defeat enemies to get gold, Gold is in using to buy various arrows and skills or upgrade weapons.
2.The most vulnerable parts is the toppart, Shoot toppart will defeat enemy in on shoot, helmet can protect the head.
3.Different enemies have different attack mode, you need deal with them in different ways.
4.Upgrade weapons and towers, buy arrows and skill challenge more difficult stages.
5.In rush mode, the enemies is infinite, kill more enemies as you can show yourself in the rank list.
It is always a good choice to upgrade weapons when the enemy is getting strong.