Getting into open source can be very intimidating, especially for junior developers. Here's a list of resources that seem to lower the barrier for new contributors.
Awesome for Beginners is a project that lists other projects that have issues for beginners or new contributors. It even tells you how each project labels their issues. For example, ember.js's label is "good for new contributors"
Up For Grabs is another way to find tasks curated for those new to open source.
Although they don't tweet too much, Your First PR is a twitter account that tweets starter issues.
Once you get started, take Shubheksha Jalan's advice and start blogging about your experience as a new open source contributor.
And if you're reading this because you thought this was actually a guide to open-sourcing your project, How to Get Started with Open Source is what you're looking for.
Shoutout to Jesse Ditson for sending me a big chunk of this list and for being so thoughtful and encouraging, all the damn time. He works for Attic Labs and their project, Noms, a decentralized database, has starter issues labeled "GoodFirstBug". ✌️