How to Deal with Design Changes and Update Requests?

This what contracts are for.

You need to define the scope of your agreement and set charges for various updates etc.

IamNameless may have some input in regards to this...check out his offer here on the forum...along with other who have been in your situation in the past.

Simple, you charge them your hourly rate.

Could also offer monthly maintenance plans. Such as: $50/Mo for up to 1 Hr of work, $100/Mo for up to 3 Hrs of work, and so on. I like the maintenance plans better because it's guaranteed income and helps you better estimate the amount of hours they need on a monthly basis.

outsource the routine changes, or have them hire a PT person hourly, or train a current employee.

Are you charging a monthly fee for both hosting and maintenance? $50/mo seems to be the sweet spot.

I don't think charging an hourly rate is in your best interest when it comes to this. Instead, you should be setting the proper expectations when they pay. Allow for changes, revisions, etc. but once they approve the site and it "goes live", included in the monthly hosting/maintenance would be minor changes like text/content changes, possibly picture uploading if they have a gallery.

Prices, opening hours, stuff like that, just give it to them. That's easy, takes 1 minute to do, right?

Now the color changes and adding pages, that's where the problem is. Color changes, that's a design issue, if the site went live and they approved the design then that is not included in the monthly hosting/maintenance.

Adding pages can easily be solved by adding different pricing packages for your services. For example you sell 5-7 page website for $999.... if they want to add 3 pages they move up to the next tier, of 8-12 page website for $1,399, they pay the difference of $400.

Make sense?

You should definitely have a contract signed before doing any kind of work. Describe everything in your contract, with detail, so that there will be no confusion regarding what the 'final product' will have to look like. And if the client wants additional changes, charge them. Set up an hourly rate and charge according to what that is.

Everyone has given great advice so far. Make sure that before the site goes live you have documented approval that they have accepted the site design and content and approve it going live with a paragraph that restates the cost of updates and changes from here. If you're doing a stage by stage approval as the site is built, get the same OK from them in person or via email to protect yourself and especially your time. You'll learn how to spot the whiners and "just one more thing" people as you get into this. The ones who really eat your profits are the "I'll know it when I see it" --- they cannot make a decision, constantly come back after they've "talked to their friends," and are perpetual time-robbers. Prep the interim stage approvals and "go live" approvals so it's part of your process/system. And have your standard choices for after-launch "updates and maintenance package" as mentioned earlier in the thread. Cheers to your success!