Lavinthal Discards..(prefer to use on  first discard only...)

 

a) A relatively low card shows a preference for the lowest of the two remaing suits...

b) A relatively high card shows a preference for the highest of the two remaing suits...

c) Advantages of Lavinthal discards:

   - allows suggesting a shift to a given suit from two other suits

   - avoids wasting a high card in a suit you wish your partner to shift

   - reduces the possibility of falsecarding by declarer

REMEMBER...You don't want the suit you drop...
                         You are never indicating the trumpsuit...

Therefore...If Spades are trump and you cannot follow suit...

drop the 7 of diamonds to request the lead of a Heart...
drop the 2 of diamonds to request the lead of a Club...