Well if you asked my stepdad, he'd say, "Whiskey and the floozies."
Seriously though, I think manly is in the eye of the beholder. Some guys feel manly by beating up women and drinking. Some guys feel manly by going to the gym 5 days a week. Some feel manly playing softball. Others feel manly by playing video games or gardening or painting pewter figurines. It seriously is something you need to decide on.
So pick out a bunch of various hobbies that your other guy friends do and see which one appeals to you.
I used to play this Live Action Roleplaying Game in my 20s, where I got a rush out of playing a character who was a funny but blunt individual. It gave me a great feeling of control over myself and in return I would feel more confident in my regular day activities.
After that ran its course, I turned to learning how to hunt with my dad and my brother-in-law. Met some mutual friends of my brother-in-law and we all get along well today. I enjoy the time out with them and get the same confident feeling in myself regardless of whether I actually take a deer or not.
Over the last month, I decided on hosting a LAN party (Competitive Computer Gaming Party) for about 16 of my friends. I realized that I needed to make room and organize our basement which looks like the show "Man Caves" meets "Hoarders." Planning the cleanup project with my 13 year old son and starting to clean it out last Sunday really helped me get that confidence feeling I had doing those other activities.
So, to quote the character, Bishop, from the 2005 comedy movie "Waiting":
"..So, when things in your life become stagnant - you know, you're no longer happy with what you're doing - then you figure out what's important to you. Then create your own penis-showing game. "