I'm sure there are many books and web sites, but first hand info would be best.
Plan your carving. Solid blocks, hollow blocks, head position..... Layout your pattern on 1/2x1/2 grid paper for detail, side,front and top. Cut out and attack with a rasp and file anything that dosen't look like a duck! Do a prototype first. Make heads and keels seperatly, Keep feather profiles low, but carve them in. It adds a lot of detail, Class. Allow more time than you think you'll think you need. Sign, number and be proud of your work. Don't point out what you think are flaws, others will never see them( they will be to impressed). Wood deeks are very heavy but very satisfying to use when you have made them yourself!