I see, thanks guys!

Actually, there isn't really a set of rules or guidelines for adoptables, you can do them however you like ^^

As Alphawolf12 said, you can offer them up as first-come-first-serve, where whoever asks first gets the adoptable, but you can also offer them up as draw-to-adopts, or ask them to try out with a bio, story, etc. Another way of selling adoptables is by asking for money or site currency (such as Deviantart's Points) in exchange for the adopt.

You can post them on the forums, or if they are source related (eg. fan children of official characters) they can go in your gallery. You don't have to just post them here on AS though, adoptables exist all over the internet.

As for the last question, you can do this however you like! You can draw the adoptables, render them, colour a lineart or base, just as line as you have permission to do so

So yeah, go crazy! There aren't really any restrictions for designing adoptables :3

What Alphawolf12 said, but now people are only allowed to post them on the adoption forum here- /board/adoption-f31.html
You're probably automatically logged into the forums, but if not, log in with your same username and password that you're using now.

Yeah, that helped a lot, thanks! I never realised it was as simple as that!

First question: People usually do first come, first serve. (I do that) the first person to ask for the adoptable gets it.

Second question: You post them on your gallery and if you want, tell people you have some adoptables.

Third question: Yep. That's what I usually do.

I hope this helped!