You need to promote your forum in social networks to get good visitors who may sign up as members. Buying some paid banner advertising in popular forums with high traffic will also help get more registrations.
Sharing the link to your forum with friends is a good way of getting new members. Doing post exchanges with members here can help get new members and posts as well. 🙂 Also if you haven't yet promote your site here! It may take sometime to get new members, but remember Rome wasn't built in a day. 😛
Regarding a good way of registering on way, I can say that there is no way.But if you want to promote your forum or your referral link, facebook, twitter and yahoochat is the best way to get referrals or you may take help of the forum if it permits you to do so.
Try to get the word out. If you build it like a community, people will come. Stay positive. Creating your first forum is more about learning how to do it than making money or whatever secondary things that come afterwards.
Also, have patience 🙂