Email Outreach for Backlinks

Hi. I'm doing SEO for someone at the moment. More specifically backlinks for a whiskey website. I have come up with keywords to find similar sites that sell whiskey merchandise. However, I am not 100% sure about the email outreach part. I plan on asking the sites I have gathered to ask if they could provide backlinks to the site I am working on by checking it out. Site will be SEO optimised so blog included. My question is: is there more to the backlink email outreach than asking them to do a backlink to the site so that traffic increases? If so, what are the methods? Any tips are appreciated.