Is there a good way to break up with someone?

I had a couple of dates with a guy... he's nice & all but I'm not feeling the spark whereas he is... I'm finding him quite childish but initially I thought that was down to nerves but the childishness hasn't faded... I don't want to lead him on but don't want to continue dating him... how do I let him down gently? I don't want to ghost him either, I've been ghosted myself & it isn't nice...