The mistakes that waste the money
With ads, the classics are broad keywords with no negative-keyword list (you pay for “plumbing courses” and “DIY plumbing” clicks), sending every click to a generic homepage instead of a page about the thing they searched, and running with no conversion tracking — which means nobody, including the agency, actually knows which keywords produce phone calls. An untracked campaign can't be optimised; it can only be billed for.
With SEO, the classics are buying a one-off “SEO package” and expecting it to keep working (it's ongoing work, not a switch), paying for cheap link-building that risks more than it returns, ignoring the Google Business Profile while obsessing over the website, and judging the whole investment at week six — the exact point where the spend is real but the compounding hasn't started. If you're going to quit at week six, it's cheaper never to start.
Both lists share a root cause: paying for activity instead of deliverables. Whatever provider you choose — including us — ask for the monthly deliverables in writing and a report drawn from real data (Google Ads and Search Console, not a repackaged dashboard). If they won't put it in writing, that's your answer.