Flip the bike over and bounce the head of your box wrench on the chain halfway between the chainring and the cog. It's too tight if you can hear or feel a rumble in the chain. It's too loose if the bounce gets sloppy. Over time you will come to learn what the bounce in the sweet spot feels like. Using a chain tensioner allows you to dial in that perfect "pitch," then tighten up your lug nuts. Good luck.