Direct Answer
To hire a reliable commercial glass & curtain wall installation contractor in New York City: (1) Get 3 written quotes with line-item breakdowns, (2) Verify NY license at New York Department of State (dos.ny.gov), (3) Confirm active general liability and workers' comp insurance, (4) Check Google and BBB reviews specific to New York City projects, (5) Never pay more than 10-30% upfront — never pay in full before completion.
Full Explanation
Red flags specific to New York City contractors: no physical New York City-area address, pressure to start immediately, cash-only payment demands, and license numbers that don't verify at New York Department of State (dos.ny.gov). Seasonal demand during summer brings out less reputable contractors.
Local Factors in New York City
📍Verify license: New York Department of State (dos.ny.gov)
📍File complaints: New York Department of State (dos.ny.gov)
📍Homeowner protections under NY consumer protection law
📍BBB Greater New York City chapter for complaints history