The best way I know of is to get yourself a VM and get into the weeds; try to configure a system to your liking.

Follow the NixOS manual. The Wiki is unofficial; often opinionated, out of date or just plain wrong. Take it with a grain of salt. The canonical source of documentation is the NixOS manual and it's not nearly as bad as you may have heard.

Make extensive use of https://search.nixos.org/options or man configuration.nix. Finding and making proper use of options and the module system is the bread and butter of using NixOS.

Eventhough everyone and their mom will recommend them to you for nebulous reasons, ignore flakes for now. You will know when you'll benefit from using them; namely when you need to use something outside of NixOS/Nixpkgs. You're going to have enough to figure out with plain old NixOS on its own though; I don't have external dependencies in my config to this day.

To wrap it up, make sure to ask the community if something's not working as expected: https://github.com/NixOS/nixpkgs#community