If you have recently tried to setup SSH access on a new ASA, it might not have worked the way you wanted. That is because the RSA keys need to be generated first. To do that:

And then configure SSH to be allowed from the inside interface:

Now you will be able to login using the default username and password of pix/cisco, Or you can configure AAA and setup your own usernames. Doing this will make the pix username no longer work for SSH.

First, a username needs to be created:

And then configure AAA:

Done!