I am new here, too. For me, old-fashioned phone plus email seems effective. And, I agree with @AdamLPW . Knowing at least a little something about your buyer/prospect before just reaching out is pretty critcal.
Also critical to long term success is having a firm grasp of the problems my product solves, the impact on my future buyers if they have those one or more of those problems, and possible underlying causes of those problems.
Then I can tailor all my messages, both calls and emails, around one potential problem at a time. If I create my messages correctly, the buyer will reach out if they have that problem - and want to solve it. If there is no response with one problem, I will give it a rest, then move on to the next problem I solve.
When buyers reach back, they know exactly why they are reaching out, the problem they want to solve - and I know I can collaborate with them to build a great solution. Definitely a win-win.
And, I imagine this could work well with social media platforms, too, though it may be harder to personalize.