As /u/Booney3721 said, you still want to learn to identify as many ducks as you can so that you can identify before you shoot.
You also want to learn when certain ducks are going to come through. In my state, Mallards and Blue-winged teal are the two most harvested.. but the Blue-winged teal are going to be long gone by the time we start seeing mallards.
Likewise, there are birds on that list that are below well below 10k harvest numbers that we saw a TON of toward the end of last season.
I recommend picking up a small identification book and studying it. I have a this book in spiral bound that I keep in my blind bag: https://www.amazon.com/Waterfowl-Identification-LeMaster-Method-Richard/dp/0811729826/ref=sr_1_1?ie=UTF8&qid=1492797039&sr=8-1&keywords=lemaster
It shows the different stages of plumage of each species, with approximate dates for when they go through each plumage. Also shows their typical height while in flight. Pretty handy little tool.
“I think” is a ticket in every state I’ve hunted in. Failure to identify in hand.
May I recommend
https://www.amazon.com/Waterfowl-Identification-LeMaster-Method-Richard/dp/0811729826
Happy hunting