1. A LOT of or a hacker.
2. A currency
4. Something FUN to do.
Okay, self explanatory, but try using Invedit or sending off lackeys to mine for cobblestone. Dirt is also useful, but Cobblestone is more prefered. You can also throw your newbie players right into the heart of enemys.
I try to use Gold bars, but you can use something else that is also rare like:
Pork and/or Cooked Pork (Cooked being better) Advantages: Self-renewing. Disadvantages: Easy to find, can 1-Up Pork easily.
Diamond Bars. Advantages: Rare and is good for amour and weapons, like olden times. Disadvantages: Almost impossible to find.
]" title="-<->" /> Feathers. Advantages: Between Rare and Common, and is useful for arrows. Disadvantages: Almost none, but is a little more on the Common side.
Wool. Advantages: No use yet, and looks great in houses. Disadvantages, 'money farming'.
Flint. See Wool.
Coal. (Thanks to City Builder!) Advantages: There is an abundant amount, but is hard to find. Also, it has uses. Disadvantages: Only if you hate coal.
Use the money accordingly by using Q to drop the money onto the peddler's head(s) and the peddler dropping the item onto the buyers head. Easy!
Listen, community and people AREN'T RARE. Just get your friends and build a (slightly) cool area, then publish a video tour of it on YouTube or Facebook. Doing this will allow people to flood PM you with 'WUT IZ UR IP LOL' messages.
Make sure you are ALWAYS doing something. It is much more boring to get a premade map then to make it all on your own. Call council meetings almost every week, and make sure you get some adventure included. Examples are:
 Recruit a griefer to remove all torches and coal. Let the monsters come into the community. Fight!
 Try sending out someone to claim, let say, 10 diamond blocks to get money.
 Move the kingdom to a 'summer home' for awhile.
You can set rules, so people will act better and LIKE the rules, because it rids of some noobs. You can make Spleef arenas to have griefers in a death sentence. You can find two rule breakers who SHOULD be exiled and throw them into a Spleef fight to exile the loser and make the winner come back again. Endless possibilities!
 Try to make 'noob' chests, where newbies can grab some items to get started.
 Make lots. Don't share, just offer lots for sale, and sell supplies.
 Divide into reigions, like making one a 'noob' land, where newbies can start out, and buy lots in the 'Player' land once they are ready.
 Protect from griefers by playing your server for an hour or two at a time daily, to look out for griefers.
 Make entertainment. People are always waiting for the boredom time when Minecraft just snaps. Make 'Spleef' arenas where entertainment is charged as always.
 HAVE FUN!