General
Every Game need new concept and ideas to make people interested in it , because if they saw the same concept & ideas of another game they will leave yours and play with the original so rule number one: Don't Imitate Other Games!
Review Games
To get new concepts without realizing that there is already a game and it been popular nowadays, you should always review the game world in specific platform like: What are the popular game? What ideas and concepts are used before? Can this game get new concepts without being a copy of it? These questions will help you not to make games with old concepts.
Original & Inventive
Always find a new inventive and original ideas, be opened for new experience and review it and see if other would like it or play it. Don't make alike games, like if you want to make an adventure game don't use Mario Bros concept and story-lines, be creative and make your own stories, power-ups, concepts, etc.....
How to get ideas
See what happen in real life, take sources from dreams or just imagine things and ideas. Like: "I want to make a puzzle game. Its have levels and achievements. I should not imitate other game but I can get some ideas from it. That right I have an Idea! The game will be about...." then make a demo and let some close people see it if they like it.
Perfect Team , Perfect Game
We all know we can't do anything alone, we need other people to help us. "One hand don't Clap" Find a good team to start with so if you are a game developer and game designer find someone who can make cool graphics and amazing sounds. Alone your game will be nice but not Wow!
Before Publishing
After you finish the game with your teammates, review it, fix it bugs, see what get wrong and tell yourself: "Are there something missing?" Then before publishing, find an awesome description for your game. because a good description will attract people and make them play. That's All.