Ask web designers and developers the important questions before hiring them to build your website.

Find out how long they have been in the business.
Knowing their number of years of experience will guide you into determining whether or not they can handle the job.

Find out the web hosting platforms they use.
Platforms like WordPress and Squarespace are recommended because they are easy to use. For example, you can conveniently make changes like updating your text and dropping pictures on these platforms yourself without paying anyone to assist you.

Identify their style.
Find out if they have diversity in style. Note that a good designer can adapt to various styles while still keeping to conventions that work for everyone.

Find out how proficient they are at making changes to website templates.
The point here is to determine whether or not your designer or developer can handle the task of website customization.

Find out if they need any extra help.
For example, can they set up the database and server for you, or will you need someone else for things like these?

Ask them what happens in an emergency and their plan for ongoing maintenance.
Do they have regular support hours you could reach them? What's their response time in support situations? Will they help you recover your site if you are hacked? Will they assign anyone to help you with ongoing site maintenance?

Ask them if they have other skills they could bring to the table.
Are they experienced in things that can boost your online presence like video production, public relations, traditional marketing, as well as writing and editing?

Find out their process for developing a website.
There is no right or wrong process, but experienced designers and developers know their website process like the back of their hands and can recite it from memory.

Ask them how they are going to test the website after building it.
Will they rely on their instincts or undergo a rigorous user testing process?

Find out when they will be able to get started.
Most web developers are busy but likely fit you into their docket a few weeks after an initial meeting.