jongearz said:
How to make them happier?!?
Luxuries. Lots of newer players go for temples... I rarely mess with them.
In the early game, expansion is your priority. Make sure you identify luxuries in your early scouting, and get settlers to those areas to get those luxury resources within your borders. Some of your early worker priorities will be roads. Connect your cities to each other, and connect the luxuries to your road network.
Other things you can do:
The luxury slider. Slipping it up to make some citizens happy can help.
Some forms of government will allow you to use military units as "MPs", giving you one content citizen per unit garrisoned in the town. In Despotism you have a limit of 2 MPs per town.
Specialists: As a general rule I will only hire entertainers in serious circumstances (War Weariness in representative governments). Tax Collectors and Scientists are deducted from the unhappy citizens. So if I've got 1 happy citizens, a content citizen, and 2 unhappy, I can convert 1 citizen to a tax collector or scientist to get one each of happy, content, unhappy, and specialist.
Do not underestimate the power of Marketplaces. Once you add a third type of luxury resouce, the Markets have a multiplicative effect on happiness. Connect all 8 lux resources to a size 12 city with a market, and you're going to have a bunch of happy citizens.
Good luck!