Let's start with the first way to identify a potential foundation problem. Without even going into the basement we can identify problems or potential problems.
First, if the doors don't open properly or if they don't open the way they used to, if there are problems with the jam working properly. You can also look at the molding around the doors to see if they have pulled away or buckled at all.
The next way to identify a potential foundation problem is as you are walking around your house or a house you are considering buying, look a the corners of openings. What I mean by that is, look at the corners of windows and doors or openings going to one room to another. Look at the sheet rock and see if there are any cracks in them.
Another thing to do is look down at the tile and see if there are any cracks in the tile. It may mean that there are foundation problems or that they didn't lay the tile right. But, this is something that you should further investigate.
The fourth warning sign of a potential foundation issue is the windows. If the windows that were working properly are now hard to open, close and lock, this may be something that you should further investigate.
Next, go outside and look at the exterior molding of your house. See if they have buckled or pulled apart. Also, look at the siding and see if any of it has buckled or have space in between the pieces. These are also signs that you should do some further investigation.