Use content warnings when appropriate Some people might be triggered by certain posts, so it's a good idea to hide them behind a content warning or CW. Often used examples for content warnings are "mh-" (bad mental health), "ph-" (bad physical health), "uspol", "depol",... (politics) & "corona"/"covid".
Don't repost retweets to the Fediverse There are Twitter-Mastodon crossposters. It is generally okay to use them, but try to avoid giving Twitter credit on Mastodon. Generally it's best to crosspost from Mastodon to Twitter but if you have to do it the other way around make sure you don't crosspost retweets and don't crosspost posts that contain Twitter handles.