SWEP making, where do I start?

I’ve downloaded, requested, tested and commented on hundreds of SWEPs by now but for the life of me I have no idea where to start when it comes to making one myself.

For instance I have always wanted to see these FPSbanana skins.

Now that we have a couple of skins to choose from. How exactly do I go about turning them into SWEPS?
It may sound ambitious but I’d like to have them implement iron sights and proper 3rd person holding animations to boot.
Currently I plan to just start with the first one:

I’d take a look at this here article: http://wiki.garrysmod.com/?title=SWEP

Look at some basic SWEPs off of garrysmod.org, and you can begin to get the general idea of how these SWEPs are structured. I’ve made a decent amount of my code just by copy-pasting somebody else’s stuff and then changing the details.

How do I make an addon?

Look here and then look at some of the addons that you currently have to get a deeper understanding of at least the format.