"Start your cities near rivers.  It will eliminate the need for an aqueduct to grow beyond a population of 6.  All irrigation must start at a river, too." - TEM

"Fortify your units behind rivers to take advantage of an additional 25% defensive bonus." - TEM

"Whenever your research is at one turn, set the % as low as possible while staying at one turn. You will still gain the research and along with more money in the same time." - stormcrow

"When attacking an enemy city that is fortified with strong defensive units, use an expendable (weak) unit first. You will almost always lose the first attack regardless of what you use, so save your stronger units until the first unit is destroyed. I know the rule book says there is a mathematical formula, but it is not all chance which can be proven. There are certain times the game will force you to lose a battle, no matter how many times you save and restart." - cirith_ungol

"When you are fighting a war and you are conquering the enemy's last city you should surround it with strong soldiers so no settlers or troops escape to build any new cities." - will

"Trade a civilization just about any thing for 20000000 per turn even if they don't have the money they will still pay" - JTB