Was just looking at Madison via Mapquest to orient myself. Don't see much there that can help me so I will give you some basics.
I am not that familiar with the area you mention. Furthest N. I have ever been, was once to Oshkosh for the airshow and other than that, Watertown, Occonomowoc, Delefield... which could be fairly similar and close. Also, it has been some time since I have been up past Lake Geneva. Last time there I was amazed at the growth and how things have changed. Got lost on the way to Delafield a few years back. Going through vast areas of farm fields and came up on one after another subdivision of new homes and industrial parks. So, my vision of the area, the memories of farms and woods, lakes and wilderness, could be a little off from todays reality.
I went to school in Whitewater and Lake Geneva. I go to Delefield from time to time. I suppose I could relate a little of my visions of those areas... into some of what I might suggest.
First check with local and state ordinances and laws about whether you can detect in certain areas. Usually, sand is pretty permissable, as might be trails and bare dirt areas. Campsites etc. But, you might often run into some resistance when it relates to areas where there might be wildlife issues or vegitation. Also, it seems that, perhaps, large areas, in your area, might be considered State Parks or Forests. Ie., The Kettle Moraine. Don't know how close they come to your area. Areas might be under the control of DNR or federal or state parks services. So, check with them to see what and where is permissable and what restrictions, procedures or regulations they might have.
I found this while doing a little looking.
http://dnr.wi.gov/org/land/parks/other/metaldetect.html . Cities and Counties might also have specific rules or restrictions so you might check with them.
So, all that being said, I would suggest starting with areas that are easy to search and do little harm. Seeing that you are a beginner. This will allow you to get most use of the detector with limited available time, get more familiar with it and develop proper recovery skills without doing much damage to grass, plants.... That is going to be a big concern in areas you search. Vegitation and Wildlife preservation. Incidentally, if you see any nests or other wildlife habitat, try not to intrude on it.
Areas that I might suggest to start are swimming beaches that might have sand, gravel or open space with little vegitation. Places where people might lay in the sun, walk along the water, have a picnic. fish or prepare their boat for launching.... Tot Lots or playgrounds where there are wood chips or sand. Search areas where people get horizontal or inverted. Swings and jungle jims are good as users will often hang upside down or get into a high arc on a swing where items can fall from pockets. Volleyball Pits that might also be sand are good. Along with many types of athletic facilities where people might pile belongings on the sides, get active and maybe loose jewelry or money from pockets while jumping for a ball or falling on the ground... After you get comfortable with whether your detector is adequate and that your abilities are up to par, try some athletic fields or parks where you can look for items in the grass and lost along sidelines, under bleachers etc. Spectators at baseball or soccer or football games often loose items while sitting around. Do you have any fairgrounds or parks where festivals might have been held? Drive in Theaters or places where ther e might be concession stands. Search where people might have reached into their pockets for money and dropped some on the ground. Again, check with parks departments, or school districts before searching. Especially along the manacured and maintained fields. Some high schools and colleges have elaborate and expensively built and maintained fields behind fences. If you have open access, You might be able to search the surfaces but there might be an intolerance for any digging. Especially on the field.
Another possibility comes to mind. Street projects or construction sites. When they grade off land for development, remvove concrete or asphalt, tear down older structures... they often expose items that might have been covered too deep to be detected. Or items that were innaccessable due to being under concrete. If you have the opportunity, see if you can search dirt piles that were scraped off or the bare areas that have been prepped for paving or construction. Contact the property owner or developer etc... before entering construction sites. Some public projects like streets, a new park, parking lot... might be open fair game if not fenced off.
If you know someone with a farm, or old homestead, check around there. Look for areas where people might have been actively working or recreating around the property. Areas where trash might have been discarded, back in the days when there wasn't waste collection. A lot of large properties might have had on site dumps. There are often some good items that can be found in these areas. Maybe not particularly valuable, money wise, but possibly items with a good glimpse into life in another era. Relics of old farm days... Old bottles and such. Look for areas where there might have been a clotes line. When clothes were hung out, if coins were in pockets, they might have fallen out when the pants were hung from the line. An old farm house with a tree about 15 feet from the back door, or a couple trees about 15' apart.... There might have been a clotes line strung between there and another post or tree, or maybe the house. Swimming holes, creeks or ponds. On a hot day in the field, a farmer, or maybe the kids, might have removed a shirt or some other clothes to cool off with the water. Items cold have fallen from pockets. Areas where children might have played. Sandboxes... Places where old toys could have been burried. Areas between a house and a barn or garage. As would be a case with any place along a park or beach as well, anywhere that someone might reach in their pockets and pull out keys, other items often fall out at the same time. Coins, Jewelry, Lighters, Keychains.... all might fall into the dirt. Maybe look around a barn or corral... or where there may have been animal pens at one time. Might find old, discarded horseshoes or nails.... or other ag related items.
Then there are possibilities of cache locations. In days prior to and especially following the depression, people didn't have a trust in banks or even their neighbors. Not having safe places that they were confident in keeping things, or when burned by the depression and not having anything to live on during hard times. People would often hide valuables. Some pointers that I have read are places visible from the windows of the house so the owner could keep an eye on them. Burried in places that nobody in their right mind would try and dig. Say an animal pen full of messy pigs or an angry bull. Dog pens with German Shepherds or other intimidating dogs was one specifically mentioned. Wells, Out Houses.... Look for a single large tree in the middle of a wide open space. Sometimes someone would hide a cache and mark the location by planting a tree over it or putting a large rock over it. Building a fence with the corner marking the location of the cache or maybe burrying the cache in the corner of the foundation of the house....
If there are wooded areas where there might have been old cabins.... look for signs of foundations and other signs that someone might have camped there or sometihing. Items could have been lost in those areas also.
As for railroad tracks. I have read that they are, usually, not very productive. However, Look at areas around old switches or sidings. Locate where stations would have been. These are areas where passengers or train crews may have mingled around, waiting for a train or clearance from a signal to proceed. Train crews might have parked a train on a siding and had to do some work on a car. Ie., crew loosing or leaving tools or other items or belongings, in the active performance of their jobs.
