This Tutorial is Simple: (Mostly Applys to SMALL-ISH Servers)

FIRST IMPRESSIONS [COUNT] - When people join a server, they expect you to have a sense of happiness about them joining. So do, and Don't do the generic "Welcome!". Use they name, maybe even give them a tour around spawn, and into the wild so they feel comfortable.

INTERGRATION - After you have aqquired some players, spend some time with them, maybe go on an adventure with them, or a hunting or mining trip? Maybe PvP them (In Survival), congrats them at achievement gets and milestones, and just in general be considerate.

HOST SPECIAL EVENTS - Whether this be a drop party, a sale at the shop, a nether fortress raid, a survival games match, or teaming up against the enderdragon, you can aways bring the community together even more.

GET TO KNOW YOUR PLAYERS MORE PERSONALLY - Via FB, Twitter, Skype or whatever, maybe make a special groups just for your community, maybe get to know everyones names, this all make the community happier.

BAND TOGETHER TO SAVE THE SERVER - In fear of a server shutting down that your dedicated players have spent so long on, you may ask around for donations, as "every little helps", maybe using a free pet, or a prefix as a lure?

CELEBRATE ANIVERSERYS/MILESTONES - Who doesn't like a drop party when the nth Player arrives, give the community that same feeling at maybe the 1 year aniversery, or maybe just of real life holidays (firework night?)

SO - "COME TOGETHER, RIGHT NOW, DIAMOND ME!"

DIAMOND, SUB, AND FAVORITE, AND ALSO COMMENT!