For a population boom switch your goverment to Democracy and make sure your tax rate is 30% for taxes 40% for science and 30% for luxuries.
Then your people in your cities sould turn from size 3 and size 13 in ten goes just make sure you have enough food.
Don't start a war or your people will get unhappy and won't grow and remember if you leave your people in a civil disorder for more than two turns you will have a anarchy!!!
More tricks, tips and cheats for this game are right here - Civilization 2 cheats
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