What's actually included in the base price?
Have the venue list it. Compare on what's included, not on what's implied.
What does the weather backup look like?
Specifically. Where would my ceremony be if it rained an hour before? Walk that space.
Who's on-site the day of?
If it's not the person giving you the tour, ask why.
Are there vendor restrictions?
Some venues require in-house catering or limit alcohol service. Get the policy in writing.
What's the access window?
When can vendors arrive, when do they have to leave? Tight access windows raise vendor costs.
What's the deposit and refund policy?
Especially important for dates more than a year out.