If you are doing a tournament, you get the tournament director or a representative and have them remove the spectator. In school ball, you tell the home coach to get security to have the person removed. They must leave the complex. In all of my years, I've only had to deal with spectators once as the home coach in a tourney came to me and complained that a spectator was saying obnoxious things to his pitcher and players. So I get the TD and have them take care of it. I don't worry about spectators - they are not within the lines of the field. Bottom line, as long as you tell the TD, home coach or security to have him or her removed then that's all the attention you ever want to give spectators.
As far as players and/or coaches, if they are adults: adults who are ejected must leave the complex and for this game they are ejected. (For sake of argument, as long as they are not able to be seen or heard from the field, this is sufficient and same as leaving the complex). If there is another game that day, they may return for that game, unless the league has rules that give suspensions to players/coaches for ejections. We do NOT handle that - that's for the league to decide.
If the ejected participant is a player who is a minor: They are restricted to the bench in school ball (we are not to have them leave..as an unsupervised child we would not send them away.) In tournaments, we tell the coach that they must leave the dugout if there is someone who can supervise them (Is mom and/or dad or another guardian there?) and if not, they are restricted to the bench. Of course, we do not want to hear them anymore from this point forward - but then again, once they are ejected, I no longer hear them anymore anyway.
As far as league games, it depends on the league rules but I would expect it to be treated the same as a tournament.
Hope this helps.