The first strategy to control these seedlings is to rake up as many of the helicopters (samaras) that you can. This will keep at least some from germinating.

 Once germinated, maple seeds are easy to pull by hand, it's just a bit labor intensive. Catching the seedlings early makes them easier to pull. You want to get root and all. Mulching gardens could also help.

A non-selective herbicide, like glyphosate, can also be used.  Be sure to only spray on the intended seedlings as anything else it is sprayed on will also be killed. Tree seedlings growing in flower beds and other landscaped areas will need to be destroyed by digging or pulling.

 
Maple seedlings in the grass do not withstand mowing.  Repeated mowing of the lawn from spring to early fall should destroy most of the tree seedlings growing in the lawn.