Within your business, it is vital that you maintain customer satisfaction, so missing bookings from an issue that has gone to print is a massive hindrance for the company.
A really useful way to reduce missed bookings is to use a Flat Plan. A Flat Plan is essentially a drawing of your magazine, you simply place any received bookings into relevant pages. This will allow you to see what bookings are placed, where the gaps are and if you have missed any bookings. This should help you to visualise how your magazine will look when it gets published.
If you have the facility to do so, you should also close down an issue once it has gone to print. This will stop any sales people from adding bookings after the magazine has gone to print, and therefore reducing missed bookings.