No matter the niche, you should be using some sort of newsletter subscription service for your website. Once your visitor subscribes to your newsletter, your in their circle of trust. They are welcoming you into their inbox.
The issue is the fact you want to convert visitors to newsletter subscribers. Of course, you can do this with pop up optins, but a very common and effective way is from your sidebar. A lot of people will say that you should offer something of value in order to entice yours visitors to subscribe.