For single-user Mastodon instances, it really helps to become mutuals (you both follow each other) with some people on a few big instances. That will establish federation between your instance and theirs. Other things that can help are:

• Interact (like, boost, reply) with interesting posts from another instance
• Fill out your profile! That side of fedi tends to distrust blank profiles.
• Write and sticky an introduction post, for the same reason as above.

@sexy_peach@feddit.de does a great job of explaining things.

One thing I will add for single-user Mastodon instances: joining one or more relays can be helpful. You can find a list of relays here: https://relaylist.com/

I'll also post the information on that page, because I think it bears being emphasized.

Pros:

• Increased activity in the federated feed of your server
• Improved hashtag results for users
• Expanded reach for users as posts are sent to all participants in subscribed relays

Cons:

• Increased media storage requirements and cost
• Increased resource demands
• Cost and performance of smaller deployments may be negatively impacted
• Increased moderation responsibilities

Finally, the participants number does not directly correlate with the load adding a relay cause. It is best to review the servers participating to gauge activity. For instance, relays that have a few large, very active servers subscribed will impact your server's resources more than relays that have numerous small servers subscribed.-----

No, your not shouting into the void. It gets shown to your followers and to their servers (in the public timeline). If your toot is boosted it will show up on all the servers that it needs to to be shown to the people that follow the account that boosted your toot.

Mastodon basically works on a need to know basis. If I follow someone, my server will be sent all their toots, boosts etc.

This is because it's impossible to have all activity on mastodon on a single server. Even the huge ones don't get all toots!