Negative keywords stop wasted clicks. Jobs, salaries, courses, DIY, free, cheap, second-hand, suppliers, brand names you don't stock. We add a starting list before launch, then read the search terms report weekly and keep adding. It's unglamorous work, and it's where a lot of small budgets leak.
Location targeting that matches where you work. Set a radius around your base, or list the suburbs and postcodes you actually service, and exclude the ones you don't. Then check the setting most people miss: Google's default can show your ads to people merely interested in your area, not only people in it. For a local trade, "Presence: people in or regularly in your targeted locations" is usually the right choice.
Your own name, protected. A small brand campaign makes sure people searching for your business by name find you, not a competitor bidding on it.