As I am new to Unity I thought it was worth noting down any observations I have as I go. Once you become familiar with any development environment you, or at least I, tend to forget how difficult it was to find my way round when I first started.
By default Unity starts with the last project opened.
While experimenting I have found myself swapping between projects to look at different features. It is therefore more convenient for me to select the project I want to open when I start Unity.
I want the Project Wizard to be the first screen I see. It is easy to change in the Edit->Preferences form.
Enable 'Always Show Project Wizard.'
From then on Unity will start by asking you which project to open.