What should I look for in a patent attorney for my hardware product?
Confirm they're registered to practice before the USPTO. You can check the USPTO's registered practitioner search, since only registered patent attorneys and agents can file and prosecute a US application. For hardware specifically, ask about their technical background: USPTO registration requires a qualifying STEM degree (mechanical, electrical, or equivalent engineering coursework), and an attorney whose training matches your invention's discipline drafts stronger mechanical or electrical claims and spots relevant prior art faster.
Ask for two or three prosecution examples in a related hardware category rather than a general client list, and get the fee structure in writing up front, flat fee per application, hourly, or hybrid. Hardware inventions with drawings and multiple embodiments are where hourly bills most often run past the original estimate.