If you have some birds around you'll definitely have fun. There is a lot more than I can mention right now but here are several tips.
1. Keep in mind that ducks will tend to land into the wind when approaching the decoys. Position yourself accordingly.
2. Conceal yourself and minimize movement when the birds are working.
3. Try to have the sun at your back. There are several benefits of this.
4. Broadheads are best, even on smaller ducks like wood ducks. Magnus Bullheads are a decent option for clipping shots but you will most likely not bag a direct hit.
5. Bring a retriever and keep him tied up. A wounded duck in a river can be almost impossible to catch without the aid of a dog. When you wound a duck that doesn't have an arrow protruding from it, send the retriever.
6. Shoot
7. Shoot
8. Shoot
9. Shoot some more...Your success rate is going to be very low. Let's assume you can hit 1 out of 20. It you wait all morning for those perfect, backpedalling, in your face opportunities and fire 3 shots, the odds are stacked against you. If you keep arrows flying, shooting every time the ducks give you a slight chance, the likelihood of success increases significantly. This is not big game hunting where misses are bad and feared. You need to miss a lot to be successful. That is one of the greatest tips for killing birds with a bow, shoot!