Stay positive. The papers may be full of despair, but letting that affect your attitude won't boost your closure rate. Strong belief will encourage your clients and give your own pitch more oomph.
Share the load. When the economy goes down, the risks go up. Discussing deals with the team will help make your offer more enticing.
Don't appear desperate. If you seem anxious to close, it gives the other party an advantage. Completing a deal in a tough market is satisfying - less so when you see the 10,000 unwanted widgets you accepted in your clamour to do so.
Nurture relationships. Your interpersonal contacts become paramount when the trading conditions dip. Visit people to encourage faith in your firm, and understand what the customers actually want.
Get them to commit. But not too much. In a downturn, a desperate counterparty may over-promise. Get the balance right.
Make the deal live up to the hype. Opportunities are scarce and every deal counts. Ensure that it will deliver the value you need. A good rule of thumb: make the other party happy but be sure to get what you want.