Making games is like sports or music, you have to practice and you really need to beware of what’s been done already if you want to be the best.
— Matt Nuccio (@MattNuccio)
If you are really interested in games, nothing will stretch you more than reading smart stuff outside of your own interest.
— Rob Donoghue (@rdonoghue)
Failed designs are part of the process, so don’t get discouraged if it doesn’t work! Just remember why the design didn’t work for you and try not to repeat those same mistakes.
— Chevee Dodd (@cheveedodd)
Look at the games you like, and see what works, and what doesn’t work. Sharp analytical skills are a game designer’s best tool.
— D. Brad Talton Jr., Level 99 Games (@Level99Games)

Lots of good stuff in this wide-ranging interview with Richard Garfield, designer of Magic: The Gathering and other titles:

I usually encourage beginning designers to self publish, not with the eye to making an ongoing business, but to understand the market as a whole, and get a publisher to take you seriously.

Play games you aren’t naturally drawn toward, and find out why they are loved by their fans.

Play critically, but don’t lose your sense of fun.

Pay attention to the parts of a game people complain about – can the games be changed to make those people happy without taking the soul out?

http://opinionatedgamers.com/2012/07/02/the-art-of-design-interviews-to-game-designers-20-richard-garfield/

Gamers gonna game, and your game can’t break when they do.
— Jay Treat (@jtreat3)