Assorted list of potential access considerations:
Wide doorways and hallways for wheelchair users.
Step free access (wheelchair ramps)
Enough space to maneuver comfortably inside with a wheelchair. Tables not super close together, some kind of space where one can turn around etc.
Accessible toilet. Good for wheelchair users, people who need something to brace themself against, and anyone who needs a little more time and space. (Also please don't keep it locked if you have one.)
Multiple toilets, since some people need to take long on the toilet sometimes.
Contrast colouring for stairs.
Consider trip/slip/stumble hazards.
In some cafés and restaurants I've been to the staff will shout out orders at each other ("one black coffee!" etc.). While efficient I'd avoid this if at all possible, since shouting can be triggering to those with anxiety disorders (social, PTSD etc), sensory issues and tics. I think it's also not great with hearing aids/cochlear implants.
No incense/perfume trees/strong scented items/chemicals. These can be iffy for people with lung conditions, sensory issues and allergies.
Soap and hand sanitiser in the toilets.
Pictures on menus can be amazing if you have reading issues.
Plan where and how it's possible to cater to different common allergies. Making free-from food might not be feasible but for example preventing cross contamination between gluten and gf food, not having a random open box full of peanuts (looking at you Five Guys), can be really helpful.
Also like, being able to tell the customer the ingredients of things can be really really helpful if they have a more specific diet.
Please don't make all the seating stools/backless (looking at you college physics lab).
Always good to keep in mind that a lot of people struggle with heavy doors in general.
You know those frosted stickers you can get for glass dividers and doors? Disabled or not those are great. It's never fun to walk straight into a glass door lmao. You might need more opaque ones for visually impaired people though
That's all I can think of off the top of my head.
Not all of these will be possible of course (conflicting access needs, budget constraints, location and building constraints etc.). Sometime one just can't go above and beyond and do everything and that's perfectly understandable.
Also it's good to note that if you want to cater to a certain group, like wheelchairs users, some of these things have to go together or there's no point. I'm mentioning this because I went to a place with a wheelchair ramp and then barely any space inside to move around. So one could only get as far as through the door, which was a little silly.
Hope it all goes well đź’š