Some projects try to make this easy. Check out this list / tag: github.com/topics/good-first-issue

People who know the code can quickly determine if an issue will be easy. Some things that may seem easy will be difficult, so as an outsider it’s hard to guess. Working on issues tagged good-first-issue is the safest bet that the issue won’t be overly complex to solve and that the maintainers are willing to work with new contributors.