Two Steps to Start
Create a new account
This is not necessary, per se, but if you have in mind to do more than just one or two sheets of adoptables, it might be a good idea to start a new account. This way you won't spam your watchers' inbox, if they're not interested in adoptables, and you can organize your gallery in a better way.
Be a member of Adoptables Groups
dA is a big community and the sheer amount of new deviations every day makes it hard for your art to be seen. Considering that you just made a new account for your adoptables, you have basically no watchers whatsoever so how can you get the exposure you need to sell your characters? The answer is join Adoptables Groups. By doing this you can do two things, the first is submit your adoptables to their gallery and advertise them, the second is observing the trends, what people like to draw and buy more.
It is always hard to decide how to price your own adoptables and there are no guidelines for this. There are, however, two lines of thought on this:
You decide how much you think your *time* is worth. So, if you take half an hour to make an adoptable and you think your time is worth 800pts/$10 an hour, then the adoptable is going to cost 400pts/$5. While this method is more fair to the artist (you), you should also take into account what your current drawing level is. (Remember that the buyer doesn't see the effort, only the result, and better looking characters sell for more.)
Look around, take twenty or thirty adoptables that generally look like yours (drawing style, flats/CG, anthro/animal) and look at how they were priced. Then choose something in the middle. This is a method that follows the general pricing, so it will be easier to sell your characters if you price them like this, but it also disregards any effort you might have put in the making of your adoptable.
The Secrets: Patience and Exposure
dA is a big community, among the many artists who are looking for a character to adopt there is certainly one that would adopt yours, but you can't expect them to come knocking at your door, begging you to sell them your character. You need to advertise your adoptables, submit them to many Adoptables Groups, maybe add a link in your signature to your Adoptables Account. Why do you think the big companies spend so much money on advertising?
In the end, Adoptables Selling comes down to this and only this. Patience and staying strong on your own rules.
I'm usually sympathetic when people want to buy my adoptables and tell me that they can't afford them because their adoptables *don't sell*, but I become a bit annoyed when I go to their page and see that their 20 points adoptables are all sold through trades and drawptions.
Selling adoptables can be hard and it may take a lot of time, even months, you can't simply give up after a few days! If you are not concerned about the points/money, then write in the rules that you're open for trades too, but don't write that it's *points!only* and then give adoptables out to the first person who begs you with a pretty please. Doing this is pretty dangerous for a seller because you show your customers that, with enough begging, you will yield to their requests because you have done so before. And an artist who has adopted from you through a trade, will ask you *again* if they see something else that they like.
(If you are unable to refuse them, then offer them a trade for a *new* design, like an art trade. This way you still have your adoptable to sell and you've made the other person happy.)
Adoptables Journals Series:
Adoptables, Basics for Adopters
Adoptables, Basics for Adoptables Artists
Adoptables, Writing an Artist's Description
Adoptables, Design Tutorial
Adoptables, Buying Adoptables
Original Species Tutorial
Adoptables, Original Species Confusion
Adoptables, I sold one, now what?