Trial and error. It depends on where the hole is, if it is at the surface one can sometimes tell by looking in draft render, and watching for unusual colours, which occurs when two faces are coincidental, or almost coincidental.
If it is inside the object, then, if it is not obvious in wireframe view, one can slice a copy of the object, and see if it looks right in draft render, with more slicing if its not immediately noticeable.
There is another way which may work, if you have a recent version of Pro, 2015 onwards. Use the Dynamic cut plane in RedSDK mode, (it may work in Lightworks, but I don't know how good it is), in RedSDK one can set up the dynamic cut face, and work through the object in draft mode looking for errors. I've used this method myself for finding errors inside an object.
Its tough to say for certain the best way, without seeing the tcw file.