A good way to see if there might be a sinkhole developing under your house or around your yard is to look at trees, posts etc and see if they may begin to be tilting or slanting.
Your houses foundation may also begin slanting suddenly or you may notice things such as dips, depressions or even slopes that appear in your yard.
Small ponds that appear after rain or also cracks in the ground or a pond that is draining off suddenly could be a sign that a sinkhole is starting under your house or near your house.
If you think you may have a sinkhole under your house or in your yard you should get a hold of an engineer or contact the local police at there non emergency number and they can help you get into touch with someone who can check the sinkhole condition.
Sinkholes can be dangerous and swallow you up as well as your house so be very careful.