Useful criticism.
WHO TO ASK
Actual customers, or people like them Someone unfamiliar with your business Not designers, unless you want design feedback specifically
WHAT TO ASK
Not "what do you think", which produces politeness.
Instead: What do we do, based on this page? Who is this for? If you wanted to hire us, what would you do next? Was anything confusing? Did anything make you hesitate?
WATCHING IS BETTER THAN ASKING
Give someone a task: "find out whether we deliver to your area". Watch without helping.
Where they hesitate or go wrong is the problem. Ten minutes of this is worth more than any amount of opinion.
WHAT TO IGNORE
Suggestions about colour and taste from people who are not your customers "Make the logo bigger" Feature requests from people who would never buy
WHAT TO ACT ON
Confusion about what you do Difficulty finding something Hesitation at the point of action Questions the site failed to answer
THOSE ARE FAILURES
Not misunderstandings by the visitor.