It all depends on your resources available. Personally, I'm a huge fan of Azure because it gives me options to expand later on and is fairly cheap to enter. You can spin up test sites for free if you don't mind using a *.azurewebsites.net domain and it's $10 for a basic website.

It also depends on your backend. You have to look at what the provider will support. All of them support HTML/JS/CSS, but not all will support PHP, .NET, etc.

What are you looking to do?

for simple stuff github pages is a good starting point, also usable with your own domain. Also using S3 from AWS and put your files is working really good (combined with Cloudfront to have also a CDN in place). But its always depending on your needs on the backend/API(s)

It all depends on your app needs. But for a really simple personal project or an MVP/Prototype I think either Firebase, Heroku, Nitrous or Github Pages are good places. They are easy to set up and to scale in case you need it.

It depends of your backend language. If you are using some backend language Heroku support, I suggest you that service. If don't, I suggest you soon as possible start use some VPS service, digital ocean, amazon ec2 or any other. In the future, it will be the place you will deploy it by the way. Soon as possible you get the skills, or pay someone to manage it - will be better