Well first and foremost, the most important two skills one needs is:
1. The ability to come up with an idea.
2. The ability to throw an idea out cuz it sucked.
If you can do those two, you're well on your way to modding.
This is so false it's not even funny. Everyone and everyone can come up with ideas. Putting them into practice is another matter entirely. Idea guys are a dime a dozen.
Both of you are close...yet, totally off.
As Phungus said, just coming up with ideas is meaningless. I can think of 100's of ideas for Civ mods. Thinking up practical and implementable ideas is important. Some ideas are just impossible in the Civ universe, or would bring mico-management to an extreme that no player wants to face.
Dale is dead on about the second part though. Sometimes I will plan an idea out throughly only to eventually discard it because flaws that ultimately ruin it. Some barriers can not be overcome.
There is an important 3rd and 4th requirement everyone else touched on.
3.)
The ability to learn.
Laugh, but some people have really lost the ability to learn new tricks. It happens to the elderly commonly, but people can become so one-sided in some areas that they can not learn anything about certain subjects, due to bias, or just sheer inability.
4.)
Perseverance.
Will the person run away from the first error message, the first crash? When I started XML modding I had about 3 error messages for 1 change. Did the person try to analyze the error and solve it, or give up? If it is the latter, modding may not be for you. Countless hours are spent tracking down that
one bug that causes random inexplicable crashes.
to Recap, to be a proficient modder, you must be able to:
1.) Create Practical Ideas
2.) Be able to reject ideas, at any stage of development
3.) Be able to Learn
4.) Persevere