I'm looking to make one but I haven't a clue where to start.

You'll find that most people learn modding by just opening up CivEdit and screwing around. Its even easier if you open up an existing Mod's .biq in CivEdit. So...open CivEdit, basically. If you can figure out how to edit rules, you can mod.
http://forums.civfanatics.com/forumdisplay.php?f=57

I'm thinking of just doing a FAQ for the Creation & Customization forums, I started on one some time ago and abandoned it...

I think the best way to learn how to make a mod, is to experiment. Thats how i figured everything out. If you do it that way, you'll be able to come up with alot more, like your own ideas, instead of using others (which theres nothing wrong with if they dont mind, but why not create somthing out of the ordinary-thats a good mod. I suggest just experimenting with Civ3Edit for awhile. I guess you should probly learn how to add in units and LH if you plan to do that. Otherwise, you can rename units, and create units useing old models. But past adding units and LH, i advise you to experiance modding first hand...from yourself!

How do you make Mods step by step?
most importantly though.... there are no step by step process to making a mod, its all up to you! If it were step by step, all mods would be the same! and there wouldnt be any point to having a whole section of the forums devoted to it, cause they would all be the same and you would only need one lol.

If you want to get a feel for it, like GRM7584 said, you should probly look at other mods. Download one and compare it to a normal game and see how it all came together. It's all got to start somewhere! Good luck! ;)

The Goldflash Method

1. Figure Out What civs you want
2. Figure out your unit lines
3. Make a Tech tree around the unit lines
4. add buildings and wonders
5. Do some other stuff
6. cry alot

Goldflash, your steps are quite short. ;)
I started out selecting the civs first, and then graphix for the leaders.
Then I started going through and setting up all the units, buildings, and resources I wanted second.
Then I created techs for those that needed them. Then I made techs for civilians, worker jobs, diplomacy, etc. It just keeps going really. I learned by fooling around with the editor and downloading mods and playing with them and comparing them to the original game. Best way to learn really. I'm still learning actually.

P.S.-And cry alot, or throw the computer through a window. I've wanted to do that a few times, so don't get too worked up. It can be rough if you're trying to push the limits of the game.

http://forums.civfanatics.com/showthread.php?t=114696

Shihshashah!

Very nice.