Acquire the garbage of competitors.
Purchase a competitor's product and then analyze it.
Visit the competitor's factory anonymously.
Record the number of competitors' shipments at the port or train station.
Take photos of competitors from the air and study them.
Analyze competitors' employment contracts.
Analyze competitors' job advertisements.
Ask the customer or dealer about the sales of competitor products.
Send people to participate in the operation of competitors or the operation of major customers.
Understand the suppliers of competitors to understand their production.
Bargain as a customer to understand the price level of competitors.
Talk to your competitor's customers for intelligence.
Buy the previous management of the competitor.
Check the situation with a consultant visiting a competitor's factory.