Broad match without a leash
Google pushes broad match hard because it spends beautifully. Unpoliced, it matches your 'emergency plumber sheffield' ad to searches about plumbing courses. The search terms report is where the truth lives. Read it weekly, add negatives ruthlessly, and broad match becomes a tool instead of a tax.
Performance Max eating your brand
PMax loves converting people who were already coming: it hoovers up brand searches and claims the credit. Exclude brand terms where possible and judge PMax on the incremental business it finds, not the conversions it collects on the way out the door.
Tracking that lies
Duplicate conversions, page views counted as leads, forms that fire on error. If the data is wrong, every optimisation compounds the wrongness. Audit what a 'conversion' actually is before trusting a single number in the interface.
The comfortable leaks
Locations you never serve, still targeted. Devices converting at half the rate, unbid. Ads pointing at retired landing pages. None of it dramatic, all of it monthly, and together often twenty percent of spend. Boring diligence is the highest-ROI activity in paid search.