Suit Preference Signals 

When to use Suit Preference Signals
Here are the links to the hands played in this video:
tinyurl.com/y6...
If you want a diamond returned, lead a higher spade (5S) to suggest a switch to a D. tinyurl.com/yy...
When returning a suit for your partner to ruff, the card you lead may be a SUIT PREFERENCE signal
tinyurl.com/25...
There is only one spade trick available. Overtake, so you can lead into dummy’s weakness tinyurl.com/yba...
tinyurl.com/y87...