The biggest key is to actually keep up with the numbers. If you are good in
Excel, knock out a spreadsheet to track.
A Prime Cost spreadsheet is the best. You track your beginning inventory plus
all purchases as they come in, key in your daily sales figures and it will
tell you where you are every day approximately.
Keep doing bottle counts for a while until you are confident of your inventory
consistency. Also helps to keep the staff honest if they see you counting
often.
Are you also serving food? And how big is your staff?