In a form submission context (a user submits a form, the form is "asynchronously" processed, a response is sent back to the client), what would be considered best practice to display an ajax-loader image?

1. In terms of placement in the layout (next to the submit button (left/right)? at the top of the form? etc.)

2. In terms of html (to have or to have not an empty <div>?)

Thanks in advance