Forecasting for sales success

I was making plans for this coming weekend - Tyrone V Kerry in Dublin. Should I or shouldn't I? Weather isn't all that relevant but I looked at the forecast and found another reason to go. The importance of being able to predict something accurately. (It was in 2008 that Croke park was flooded after one of the quarter finals - so accurate is the operative word.) And so to sales forecasting - the devils business. So critical to all other parts of the business, planning, buying, HR, logistics and so difficult for sales people to get it right every time - because it matters every time. Some thoughts on forecasting from the world of the sales person and the sales manager.