They would normally write to you, or e mail you, to tell you you have been selected, and may have to go to a second round of interviews, or even a third or forth, depending on how senior the job is, along with the other successful candidates on the short list.
Then they will select one person from this short list for the job.
In an urgent posting, or a small company where you are dealing with the owner himself, they may call you directly and tell you you have got the job.
However I don't suggest you call them, as it will not speed anything along, you just have to wait it out.
If, after a few weeks there is no word, and you haven't received a letter or e mail telling you you were unsuccessful, you could then call to remind them that you haven't heard back from them yet.
Then they will select one person from this short list for the job.
In an urgent posting, or a small company where you are dealing with the owner himself, they may call you directly and tell you you have got the job.
However I don't suggest you call them, as it will not speed anything along, you just have to wait it out.
If, after a few weeks there is no word, and you haven't received a letter or e mail telling you you were unsuccessful, you could then call to remind them that you haven't heard back from them yet.