Modding games is awesome for everyone!
Your honor, I bring you the exhibits Day Z, Counter-Strike and Dota.
We are firm believers in exposing as much as possible about the game for modification. We also try to foster a spirit of modding in the community and try to support their needs through patches. I just love seeing all the creative things people come up with when they have a game engine to build upon.
A dedicated modding community allows deeper understanding of gameplay features.
User mods are beneficial to everyone; first of all, the modders get experience in developing, which can become useful when they want to try a career in game development. Great designers like Jon Shafer and Henrik Fåhraeus were both modders before starting professional careers. Secondly, it is a large benefit for other gamers, who get more content to enjoy. Finally, a dedicated modding community allows deeper understanding of gameplay features, even the less visible gameplay features. The fact that our gamers can create mods makes them much more engaged, which leads both to more vivid discussions about the game features and much more creativity that we can listen to and get inspiration from.
Don't hide stuff
Gamers are smart people. Most of them aren't going to throw money at the screen just because you say it's a good game. They want to try before they buy. So let them do that! Create a demo so gamers can try it. It's just common sense. Otherwise people may pirate the game just to try it out. Some piracy is a natural rebellious response to the lack of demos. I personally feel that not creating a demo is also a signal that you as a developer don't believe in your game, because you're scared to let gamers give it a spin.
If you have delays in development, communicate them to your gamers and tell them why. Don't lie or hide information like that or they won't trust you.
Don't nickel & dime the gamers
Gamers are loyal to us at Paradox Development Studio because we constantly update our games and give them loads of stuff for free for the games they have bought, after release, even if they don't buy a single DLC.
In both Crusader Kings II and Europa Universalis IV, we are using a modular system where players receive all the patches and game updates even if they don't buy any of our DLC. Our goal is that regardless of what DLC you decide to get for the game, you should always get to enjoy the very best game that we can make. We improve the game and add gameplay features for free in major content patches, which in turn helps to keep the game evolving. We always try to give out a patch that includes new gameplay features together with each expansion, and our players keep coming back to the game to see what we've improved since last time they played. In many ways, our games becomes almost like small MMOs.
They are potential customers, not thieves!
Don't spend money trying to track down the pirates. Instead, spend the money on making it easier for people who want to pay for your stuff and reward the ones that do buy your games with free updates and free gameplay features. I repeat: Stop chasing the pirates, focus on rewarding the buyers.
I really dislike how some companies, especially in other entertainment industries, are going after pirates and try to sue them for downloading a few files. Yes, it sucks that you have put your heart and soul into a game that people play without paying for. But hunting the gamers is not going to increase your sales or recoup the money; it's just going to alienate your customers in your attempts to scare people into buying your game. And that's a pretty stupid move.