You can definitely increase your conversions if you offer the right incentives for people to sign up.
This might be in the form of discounts, ebooks, sneak previews, or an ecourse. You want to make the incentive to sign up so good that they don't mind handing over their email address at all. Many people are wary of giving people their email address, so they have to be really enticed to do so.
You also have to keep in mind that there are other marketers who are trying to get people to optin to their own list. Making the best offer you can will help increase your conversions and put you ahead of the others.