The clearest sign is when you are spending money but not getting the action you want, whether that is sales, sign-ups, or calls. Check your search term report to see which searches triggered your ads. If you see many unrelated searches, your keywords are too broad. Also check if people are clicking but leaving your landing page quickly without doing anything. That points to a mismatch between the ad and the page. If cost per conversion keeps rising with no improvement, that campaign needs a serious review. How do you tell when a paid search campaign is just burning through your budget?