You can edit the xxx.eug file (xxx denotes filename) found in the saves directory using the wordpad application.
Scroll thru the lines until you come up to your nation/side. Pay attention to { and } symbols when doing this edit.

Keywords:

treasury: edit money (limit is approx 2 billion)

city: edit city name, population (max = 999999.000), infrastructure. City must at least have level 1 wall. Fully developed city has following lines:

city = "name"
population = 999999.000
location = xxx (xxx = number)
courthouse = yes
bailiff = yes
cityrights = yes
fortress = {...level = 6}

land unit: edit name and number of infantry/cavalry/artillery each land unit has. Watch out for artillery, not too many. I prefer the following combination 30000/5000/150 (weight=50).

nav unit: same as land unit except this one is for naval

technology: edit all tech level. Set 51 for military techs and 10 for rest.

diplomats, colonists, merchants, missionary: edit number of these guys (max=6)

You can also do this dirty trick:
Set up a level 1 trading post at a neighboring state and save the game once the attempt is successful. Edit level 1 to level 6 in the following line: trading post = { "name" level = 1 location = xxx}. A level 6 trading post won't give you any rebellion problems once transformed into a colony.

Changing this line to: city = ("name" population = 999999.000 location = xxx} will automatically transform the trading post to a fully populated colony. Warning: could inspire revolt if religion is different from yours and you do not tolerate that religion at all.