Look for scratches
When going to buy a Tag, take a look at one I personally think are the two biggest issues. It won't matter if it's new or used, it's just that certain models seem to have recurring problems. First, take a careful look at the "second" hand. While most are calibrated properly, some that have been worked on by less than elite watch repairmen will be slightly off. For instance, it might stop between 29 and 30 seconds, not right on it. This may be a warning that other damaged have bee sustained. Second, use your thumb and run it across the face of the watch. Several models are not flat, unfortunately by design. This means that while other flat watch faces may just brush up against something you bump up to, that the particular model Tag you're looking at my crack instead since it will get caught. While this is a common problem among many watchmakers, if you're spending what you will on a Tag, you'll want to avoid these two problems for sure.