The most common mistake is not setting the right match types for keywords. When you set up Google Ads, you choose keywords that tell Google when to show your ad. If you leave everything on broad match, Google shows your ad for searches that are not really related to your business, and you waste money fast. Most beginners do not realize this until they check their search term reports and see how many irrelevant searches triggered their ads. In your experience, what is the biggest mistake you have seen people make with Google Ads?