Certifications matter, but they're a floor, not a ceiling. For maintenance, look for A&P/IA for inspections and major work, and specialized authorizations for things like turbine engine work, propeller overhauls, or avionics installation. Ask about factory training for your specific airframe — a shop that's worked on Cessna 340s for twenty years is a different proposition than one that's seen a handful.

For avionics, check whether the shop holds a Part 145 repair station certificate. Part 145 shops can perform a broader range of work and their documentation is easier to accept during future ownership transfers.

Insurance matters more than people admit. Ask your shop about their hangarkeeper's liability limits and whether they carry product liability coverage. For flight instruction, ask the CFI about their own insurance policy — it's not about distrust, it's about what happens if an incident involves both the aircraft owner and the instructor.

Finally: the aviation community is small. Ask around on type-club forums and at your local pilots' association before you commit to a major project like a paint job or a panel upgrade. A quick reference check can save you six months of frustration.