Read the local timeline a few days before following too many folks.
Pick some easy stuff for your first toots, like telling someone how cute their cat is :)
You will feel comfortable quickly.
@ncb Searching for, and pinning tags are a great way to find and follow like-minded people and conversations outside of your instance. You can also feature tags on your profile to make it easier for folk to find you. Welcome!
Basically, read the instance timeline or maybe the federated one (if you have eye bleach nearby) and follow any people you find interesting on it (still possible to unfollow them later).
Don't hesitate to jump in public conversations where you have something meaningful to say.
Some people react negatively to that but it's very, very rare (of course if you're not spouting nonsense when jumping in a thread).
@ncb welcome! Defining recommend just reading the local timeline for a while and replying to whatever interests you to get acquainted with how everything works
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.