Too Much Thinking
Some people play quickly. Some people think a lot before each move. Of course, this is fine -- Go is a thinking game.
But some people (especially weaker players) spend ages on each move, hemming and hawing and staring at the board.. and then make the wrong move anyway.
Lots of reasons why this is bad, but I think the most important might be this: much of Go is about feel, and weaker players need to develop this intuitive approach to the game. You need to know what to think about before you can start thinking! There's a proverb that I've heard: "A beginner should lose the first 50 games as quickly as possible." -- Matt Noonan
I think it's important here to distinguish various types of games. If one plays a tournament game, or another serious game, one usually has a certain amount of time available, and there's nothing wrong about using it (although I would prefer you don't - I get bored too easily). However, in a friendly game for fun, things are different. In those games, one should not be using so much time that one is boring one's opponent. Instead, be prepared to not make the best move you can come up with every now and again. -- Andre Engels
Recently, I have had the misfortune of playing people at both Go Clubs that I attend, who play so slowly that we are able to finish only one game a night....2.5 to 3 hours for a single club game. The most recent game bored me so greatly that I have resolved never to allow this to happen again. Therefore, when faced with playing either of these people again, I will insist upon using a clock and setting the clock to 20 minutes. -- Velobici
When I was young I played 'swop' chess at lunchtime in school. In order to discourage slow play we introduced a no stalling rule. Anyone found stalling had a standing 5 count to move or a pice would be removed. We then defined stalling as thinking. -- ~ian~
See Think movement for the opposite point of view.