The main thing about registration completion is that the user needs to care. ;)
Without having more information about your specific registration process, here are some things you can do:
Reduce the likelihood that your confirmation email goes to the users spam folder
- Use Litmus to make sure your email content will pass spam
- Set up SPF records to verify your sending IP address
- Consider using a service like SendGrid to increase deliverability
(you can also monitor open and click rates on transactional emails with SendGrid)
Test subject lines and email content
- Test subject lines, find out which ones most compel the user to open the email
Make sure the link the user needs to click is easy to
Make sure the user knows what clicking the link will do
Emotion is the driver of action, make the content of the email compelling to the user
Does the email content look trustworthy and professional?
Review your current registration process
From the way you write about it, I suspect that the process is more arduous for the user than necessary. Here are some questions to ask:
- At what point in the user's visit do you present them with the option
- Are they engaged enough at that point to make an investment in your site?
- How friendly is the registration process?
Put your current registration process through UserTesting.com -- you'll be amazed.
Maximizing conversions is an art. Think like your users. Really care about your users. Test, measure, optimize, test, measure, optimize...