This post was very helpful BUT:
I, as a Moderator or Chief Editor or CM, would never take for an on-air show a person with zero experience and zero credentials (when I say credentials, I mean past contributions to check for the quality of his/her translations).
I think new users should start from completed shows, where there is no time pressure and there can be an editor behind their back, to gently teach and correct so that they can gain experience. At least 3-4 older shows before tackling on-air.
Then, how to find a project to start with? It is not very easy.
One way is to look in Project Finder and write the moderator. But if you see that it's been almost completely done with only a little percentage left, it means they don't need anybody, they already have a team, and are working on it. Sometimes this little percentage just means they haven't translated the trailers or other clips.
One tip is, if your language is popular (for instance Spanish, Italian, French), not choose the super-popular shows because they will of course already have been completed.
Another way - the best in my opinion - is to look for moderators' names in cover pages, and write to moderators directly, asking if there is anywhere you can help. Most of them have several projects, a couple of on-air dramas and also some older ones where they are working little by little. You can also state that you're willing to make a test translation on one part, for them to see your skills.