My purpose is not give you a book review (which you can find here.), but an excerpt from chapter 10, that is a pretty good summary of the whole book. If you haven't done so, do yourself a favor and read the book, for a detailed explanation of each mentioned item.
Chapter 1. Take account of the balances of territory and power. If you are behind in territory but ahead in power, play aggressively: invade, cut, attack, and fight. If you are ahead in territory but behind in power, play defensively: play safe.Other quotes that I find insightful:
Chapter 2. When attacking, instead of just trying to kill one enemy group, look for dual purpose moves, or moves that attack two groups at once.
Chapter 3. Attack with non-contact plays. Don't touch what you are attacking. Know the eye-stealing and angle tesujis and the capping, peeping and knight's attacks.
Chapter 4. For defense, use ordinary moves if possible before you are attacked. If you find yourself in trouble, use contact plays and shoulder moves to extricate yourself.
Chapter 5. Play forcing moves, then leave them; treat forcing stones as expendable. Look for ways to resist your opponent's forcing moves.
Chapter 6. Use inducing moves to raise the efficiency of your stones.
Chapter 7. In dealing with enemy frameworks, play lightly and flexibly, taking advantage of weaknesses. Consider relations with surrounding areas (junction points, weak groups, etc.).
Chapter 8. Even within the confines of a three-space extension there are many invasion josekis. Know the meaning of the first two moves, at least, so you can choose among them.
Chapter 9. Avoid adversely one-sided and very indirect kos. In an all-dominating ko, ignore any (non-local) ko threat.
Fight, invade, and try to generate confusion - the strategy to follow when one is territorially behind is exactly the opposite of the strategy when one is ahead. p.12
At one extreme we have the player who is so jealous of his own territory that he protects it against the slightest incursion; who constantly forgoes attack in favor of defense; who loses through timidity. At the other extreme we have the player whose jealousy engulfs the whole board; who tries not to let his opponent have any territory at all; who usually ends up loosing large groups of overextended stones. These people are deluded. They understand the concept of 'territory', but they lack the faintest inkling of the meaning of 'balance'. p.12
Territory tends to fall naturally to the side that holds the balance of power. p.32
A struggle for power is basically a struggle for eye space. p.34
