Some of the best hunting is had in frozen cattail sloughs, but safety is certainly something to look out for. Often times the thinnest ice on the entire lake or basin is in those areas. Walk slow, take your time, make sure your footing and ice is good. I fall through several times a year while I try to be (somewhat) smart. Snow (insulation) can limit the ice, decaying cattails and organic matter below the ice will create some heat or energy that will limit the ice. Weather pending, you'll find plenty of safe walkable ice and plenty of unsafe ice. Just be smart, don't risk anything.
You can choose any 5 day period and as long as those dates haven't passed, then you can up them to the correct dates. I'd recommend choosing the last 5 days of the season then you have as much flexibility as possible to move those dates up to the correct ones when the time comes. I don't know if this has changed this year with the extended season, but if you bought your license after a certain date in mid-December you could use the 2nd dates for the following season.
In general, I look for (within a .5 mile or so) a food source (picked corn field that maybe has some stubble still?), winter cover (cattails), water, loafing cover (prairie), tree line (protection). Whether all of that is available on the same piece of public land, or the public land provides the hunting but the neighboring properties provide some of the other amenities that should make it an area with birds.
To me, public land is public land. WPA's may have a bit more water, GPA's may have a bit more prairie or trees. The only thing I have noticed is the school lands often times don't have much cover and can be completely crossed off on the map, but every now and then you'll come across one that holds a little pocket of cattails a quarter mile in that's a hidden gem.
Ditch hunting is overlooked in my opinion. Obviously be safe, be courteous of neighboring properties and landowners. I like to look for ditches with decent cover and a food source on both sides of the road so I can be efficient with my time and walk one side up and the other back. Then there's also road hunting, to each their own, I did it when I started out. Now I am all about watching a dog walk and would take 1 bird all day over a dog rather than 3 birds running across the road. But there's nothing wrong with it when done legally, or your tired, don't have a dog or it needs a rest, or just looking for that one last bird in the final minutes of shooting time.
Access fees.... if you are one guy and later in the season, you may be able to roll up to a house and get immediate permission for a spot here or there. IMO, there is enough public land in SD that you can get your birds on a full days of hard work that way. But it would be nice to have some private land and relationships you can build on over the years. I say this over and over on this site, 1-3 guys can reasonably expect to get a limit on SD public land every day with a bit of luck (weather, nobody else has hunted every single field you just happen to pull up to(which there's enough land that that shouldn't happen), etc.), good shooting, good dog work, etc. A group of 4+ may be disappointed on SD public land if limits are what you are after.
Read up the rule book before you go, and then read it again. Focus in on things like right of ways, how far from buildings, livestock, etc., type of shot (SD is steel on all public land).
