Where do I go and how do I start modding?

[Thunderbreaker13]

Exactly what the title says. I have never made a mod before, and I would like to start, but don't know what to do. Any help is appreciated

[Shadeybladey]

It depends what you want to do. Some mods are very simple, others are extremely complex and complicated.

But you could start by looking at the Wiki. There's a guide there on making a very simple quest called "Hello World". And people here could probably help if you get in a mess.

Make sure you always test your mods on a save that has never seen your mod. Some errors can get "baked in" and may not be fixable. So keep a save where you've never saved the game with your mod active.

On PC, pressing ` opens the console and typing

save "ModTest01" will save the game with a name you can easily recognise.

[scorrp10]

For starters, you need a precise idea as to what sort of mod you want to create.    

[greyday01]

This site is a good start Category:Tutorials - the CreationKit Wiki (uesp.net).
The video tutorial Video Tutorials - the CreationKit Wiki (uesp.net) is very useful for starting modders.
Darkfox127 has many youtube videos showing how to do many things.

Basics. Start small.
Any item, script, texture, mesh, texture set, anything at all in your mod, including the mod esp itself, should be named starting with the same 4 letter prefix. Makes searching for YOUR items in the CK much easier.

Don't change the items you find in the CK. R-Click, duplicate and give them a new name starting with your mod's prefix.

Save often. Put a folder on your desktop named mod stages. 
After completing something, save, exit the CK and copy your esp to that folder and give it a name that shows what you last completed. Go into the game and inspect what you did.
Then open up the CK and continue working. If you mess up, you can easily go back as many stages as needed.

Get used to XEdit. Open Xedit, select ONLY your mod. It will list ONLY the changes that YOU made to Skyrim. By opening up the file tree you can see everything your mod added, deleted or changed. If it wasn't a change, you wanted or meant to make, by deleting it you will remove that change. This does not change the base game at all, only the changes that you made.
Accidentally deleted all smelters from the game in your mod? Go into Xedit and delete your deletion. Magic, they are all back.  Make a practice mod and get used to deliberately messing things up and then undoing it in Xedit. It's a good idea to now and then check your mod in Xedit to see if you made any unwanted changes. Just scroll through and see if there is anything you don't remember doing. Also clean your mod with XEdit.

If you are going to be making mods, MO2 is my recommendation. Everything in your mod is contained in it's own separate folder in MO2. The base game is not touched at all. When it comes time to package your mod all its assets are already all together in a single folder for putting in a BSA (if needed) or a zip file for uploading.