"Like diamonds, games are forever." That's Kongregate co-founder and COO Emily Greer, speaking to an audience at GDC Tuesday morning about what she considers the best practices for monetizing (and satisfying!) free-to-play game players. Kongregate focuses on games with long-term potential that maintain steady profitability, rather than on games that drive in immediate spikes of revenue before trailing off. The result of this seems to be working well for the company: 90 percent of its revenue comes from the 4 percent of players who have had more than 100 game play sessions on the portal. In a session at GDC's Free-To-Play Summit, Greer shared what she called her six habits of highly effective F2P -- or, in other words, the six things free-to-play developers should be doing in order to maintain longterm users like Kongregates.

1. Be fun (for at least six months)

Fun games can run out of steam quickly, but there are ways to fight it. The biggest fundamental is keeping players busy...if there is more to do, they'll stay longer. Though Greer warns that developers shouldn't introduce too many gameplay concepts too quickly. Do it gradually, so players learn without getting overwhelmed. Greer encourages developers to "get on the content treadmill." In other words, keep pumping out new content for your games. When Kongregate surveyed its lapsed big spenders, 64% of them said they left because there wasn't enough left to do (though, on the bright side, 70% of them said they'd be willing to come back if new content was added). This might not make business sense if your game's not driving in enough money to justify the cost of making new content, though there are ways to fight this too: procedurally-generated or user-generated content, for example.

2. Be social

Every game on Kongregate is ultra-social. There is a real-time chat window to the right of the game's window, and a topic-based forum below it. While this might not work for your game necessarily, it does serve as a good example of how you can keep your game going as an ongoing conversation with your players. Guilds are huge for Kongregate. Greer says that revenue on average is 20 times higher from guild members than non-guild members for two reasons: there are social incentives to keep playing and see their friends, but there's also social pressure to make sure they're not letting the team down.

3. Be convenient

One of the biggest problems Greer sees is games punishing players for not playing for a while. "The problem with punishing people is that the consequences aren't experienced when they're gone, they're experienced when they come back: the exact behavior that you want to reward," she says. Make it convenient for your players to take a break once in a while, she says, and consider rewarding them for coming back after an extended leave.

4. Be fair

Avoid instant-win purchases. Not only is this a short-term win, it also makes your player less invested in the game...make it feel like actually playing the game is still a good investment of their time. Perhaps more importantly, she says: don't manipulate your players into spending money they don't want to spend. It will backfire.

5. Be caring

The easiest way to build brand loyalty is to put a human face on it. If a player feels like you care, they'll be loyal to you. Good community management is a key. "If may be your game, but it's their experience," says Greer. She says keys to being caring are being visible (on forums, emails, chat etc.), listening to and acknowledging concerns, being transparent and honest ("Most players are rational and understand that this game they're playing can only exist if there's revenue to support it," she says), give advance notice of changes and downtimes and, finally, don't feed the trolls.

6. Be committed

There's always a temptation that if you have a successful game, launching another title might mean you have two successful games. But that's not usually the case. "The bigger the hit you have, the lower percentage chance you have that the next game will do as well or better," says Greer. Being committed means more than just focusing on one game, though: it also applies to the price of your content. Avoid devaluing purchases with frequent discounts: you'll train your players to wait for a sale, putting yourself in a "vicious cycle" that will continue driving revenues down. "If you focus on short-term metrics, you're going to get short-term behavior," she says.