In layout setup for each layout there's a check box labeled: "Save Record Changes Automatically". If you clear that check box, the user will be asked if they want to save the record when they attempt to leave the current layout or current record.
But that may not create the most user friendly result. Even clicking a blank area on the layout commits the record and will trigger this dialog. There are layout design tricks, such as covering the entire layout body with an invisble, empty web viewer to intercept that particular mouseclick, but you may find setting up a layout of global fields for data entry and then scripting the save button to transfer the data into a new record only when the user clicks save to be a smoother way to handle this.
You can also hide and lock the status toolbar and provide your own navigation buttons to control how a user moves from layout to layout and record to record. That option allows you to control how or if the record is committed via scripts attached to those same buttons.