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