This article is from the Go FAQ, by Morten PAHLE email@example.com with numerous contributions by others.
A question related to 'How can I improve?' is 'How do I know which are
the biggest problems with my game?' The best answer is to find a
significantly stronger player (ideally at least 5 grades stronger) and
play through one of your games with him watching.
You do not need him to give you detailed comments, you want him to
point out the big mistakes that you want to deal with. They often fall
into the category of "mistakes you did not know you were making" which
is why you need another player to spot them, and you would prefer it
to be someone a lot stronger than you.
This way you can be sure that he is confused because you did something
stupid and he knows better, rather than you doing something so
brilliant that he does not understand it.
If you do not know any friendly stronger players then check out
section 4.7, or look for a teacher (see section 4.1)
Another way of trying to diagnose "mistakes you did not know you were
making" is to play through a lot (say 10 or more) professional games
trying to predict the next move. See if you can reach some sort of a
conclusion on which types of move you are consistently failing to
predict. Several Go playing tutor programs can do this. (See section