How do you start a Drupal website in a professional way?
choose one that certainly supports composer. Drupal 8 has modules that can only be installed with composer. Check if you have the correct PHP version.
as short as possible. If it is for a company, also buy the popular extensions.
create some mail accounts. This prevents you from ending up in the spam. Do not do this for a subdomain.
Preferably with a pre-installation on the Control Panel. So easy for backups and updates. There are many in Drupal 8 ...
Language / country settings / date
set it up. If only one language, remove the language code from the URL.
prevent that accounts can be created or requested
Trusted Hosting settings
adjust that in the settings.php. Then set the rights back correctly
add the code to your .htaccess file. This way, visitors who do not use the https will be led to it. Google likes this
Choose a simple theme without too many ready-made items. You have to build a theme yourself. Adaptive Theme is a happy medium. You can eg set the order of the blocks for each device. Remove all unnecessary blocks. If necessary, choose a logo and favicon.
Create a welcome page and put it as a home page. The built-in frontpage does not use anyone. Remove the home from the menu and replace your welcome page.
Make a sketch of every page that will be shown on your site. Translate it into content types and overviews.
When choosing the fields you have to work as concretely as possible. There are field settings, input and output. example image field with max resolution, focal point and colorbox.
Taxonomy or node reference.
You can also add fields to taxonomy. Know that these fields are above the taxonomy overview. A taxonomy is therefore always an overview if you use this as a link. Taxonomy is useful if you want a hierarchy in the terms or if you use eg Facets that work perfectly with these terms.
Go over this module list (from the discussions on this site). Indicate in a column what you want, filter on it and use composer to install them. Composer also installs the dependent modules, but not (yet) the third parties .. Avoid very complex modules such as Display Suite, Panels, Bricks, ... nice toys but mostly with some CSS you achieve the same.
Collect them locally on your computer in a folder of libaries. Zip and transfer it to the server. Unzipping.
Now everything is ready for input of the content. If your structure is created, test it by adding some content. If you have a lot of content, use Feeds to get the job done.
See where you have to make adjustments with CSS. Use the Asset injector.
In my opinion, the above method is the most efficient and fastest way to create a new website.