Well I find that a lot of people miss this and that's why there failing but from my point of view and what I would like in a server this is what
Staff:Kind,Respectful (No Matter how stupid a player can be) Attentive,Dedicated,Plugin Knowledge,Social Skills
Server:Non-Lag,Nice builds things that stand out, Plugins that do not glitch and are fun (Mob-Arena,War,Simple-Spleef, Heroes) something to keep players entertained, Contests, City's, Interactive plugins
Some things I also suggest are sites and forums for players to interact with like: Forums (Ban-Appeals,Post-your-creation, Ideas, Bugs) also make sure its 24/7 thats really important for you and your players
Also make sure your server is presented well you want to catch the player into coming into your server use Eye catching graphics and pics when you upload to Planet Minecraft
These are just some suggestions on what I think is a road to success

Post your Ideas, and Complaints in the comment section bellow and like always Good Luck