The fastest way to get burned is to treat a tax deed sale like a simple auction. Most expensive mistakes come from bad assumptions about title, process, timing, or what the deed actually solves.
Tax deed investors get into trouble when they use the low price to justify skipping verification. The better approach is the opposite: the more uncertain the title, process, or possession picture is, the more conservative you should become.
If the deal still works after you account for uncertainty, keep going. If it only works when every optimistic assumption is true, it is not a strong deal.