Kael's modding guide (The best, IMO)
The Newbie's Guide to Modding Civ5
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How to Add a Building: Entry Level (If you're planning on using a UB for your civ)
Add a new unit in the game (using SQL) (for your UU; personally I prefer using XML over SQL but that's up to you)
Making a custom leader use custom music (You should probably skip this your first time around, just to make sure you can do the basics first
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If you're planning on doing your own artwork:
Irkalla's "Firaxis-Like" Civilization Icon Tutorial
Leugi's 2D Leaderscreen Collage Hints (Some pretty intense artwork right here)
Sukritact's Cartography Outline
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But of course, there are many talented artists on the forums that would almost certainly be willing to do artwork for you, though I find it to be more gratifying to do it myself.
And there's many more tutorials here:
Civ5 Modding Tutorials & Reference Forum
(NOTE: This is not a place to ask questions but a place to post a finished tutorial.)