I assume that you already did a research and know who's your ideal customer. In that case, try these ways:
Good luck!
If you already have some idea of companies you are looking to target a website like hunter.io might be good for you.
Hunter allows you to enter a domain name and find email addresses for people who work there, including their position and full name. You can import these leads into an automated email tool like Mailchimp to get the initial dialog started.