Vote
Promote the server on server lists and make it easier for players to find.
Visit a site below, find a button that says "Vote," then follow the instructions on the site!
Sites
Minecraft.Buzz
Planet Minecraft
ServerList101
Minecraft-ServerList
Top Minecraft Servers
Minecraft Multiplayer
MinecraftServers.org
Craftlist
Minecraft Server List
Block Atlas
Crafty
Rabbit Server List
Rewards
Voting also gives you in-game awards, and if you vote on all sites for 7 days in a row, you get a reward that's definitely worth it.