What interface? FileMaker Pro or Web Browser?
Assuming FileMaker Pro...
One option is to set validation rules on each field that make them required fields. Then the user gets an error message if they commit the record and a required field is empty.
You can go to layout setup and clear the "Save record changes automatically" button. Then add a button labeled "save" that uses Commit Record to save the record. The tricky part here is that if the user clicks a blank part of the layout background, the record is still committed. To prevent that, you can place an empty web browser object behind all your fields and buttons, sized to completely fill the body of your layout. This option will intercept the mouse clicks and keep them from committing the record prematurely.