Always reorder when stock is down 30%. That way, you would never say "We are out".

[Fidelia]

It is one of the most pathetic things for a business to say "We are out of stock" when a customer comes calling with fully expectations to buy.
To avoid that, always make sure that you re-stock as soon as your inventory is down by 30%. What is your opinion?

 

[King Belieal]

For products that you know are fast moving, you don't even wait till it is 30% less before you restock. Even at 50% less, you can restock such products.

 

[eLdavis]

This is why it is extremely important to always check your stocks every day after work and before you begin, this way you can quickly know when the stock is going down.