Open the 'civ4config' file found in your Sid Meire's Civilization IV install directory (Default is 'C:\Documents and Settings\Owner\Application Data\Firaxis Games\Sid Meier's Civilization 4'). Find 'cheatmode = 0' and change it to 'cheatmode = chipotle'. Then during game play open the cheat console by pressing the tilde key '~' and type in any of the following and then press enter. Have either a unit or a city selected and press the following keys to activate the corresponding effect.
Display Debug Menu: Ctrl + D
Unit Level Up: (Unit) Ctrl + '+'
World Editor: Ctrl + W
Increase Gold by 1000: Ctrl + 4
Add 1 to City Population: (City) Shift +'+'
Add 10 to City Culture (City) Ctrl + '+'
Decrease Highlighted Unit's Strength by 0.2 Shift + [
Immediately Complete whatever the City is Producing: (City) '+'
Increase Highlighted City's Culture by 10: Ctrl + Plus
Increase highlighted city's population by 1: Shift + Plus
Increase highlighted unit's strength by 0.2: Shift + ]
Insert Unit/City Ctrl + Shift + Left mouse button
Instant Production Completion for Highlighted City: Plus
Level Up Highlighted Unit: Ctrl + Plus
Dialogue box to change certain nations Gold and also the Era: Shift + T