Playing Bridge is not only bidding and playing the hand. It is also Defense: preventing the Declarer from making the contract. Without doubt, it is the most difficult part of Bridge. Bidding or playing the hand can be learned in a few years (or a decade or two). But super Defense can take a lifetime (or depending on one’s age several lifetimes) to master. 
      Unlike the Declarer, the Defender is playing only13 cards. Partnership communication and cooperation is crucial. This is what makes Defense so challenging. 
     Also note that 50% of the time your are on Defense; 25% Declarer; and 25% Dummy.  So if you played Bridge for 4 years, then 2 years you are defending; 1 year playing the hand; and 1 year dummy. The year that you are Dummy you can take a long vacation, write a book or watch daytime TV.


Oh. . . pening lead.
The Opening Lead can often make or brake a contract. So its important to get off to a good start.  Even though Opening Leads might seem like a shot in the dark, (See OPENING LEADS) there should be a message for partner behind every lead. 
       The more  information you and your partner know about the each others’ hands and consequently Declarer’s, the better the Defense.  So whenever possible send information to your partner.  Good communication makes for good Defense.  Listen to the bidding for Opening Lead clues.  A good Opening Leader is a good listener. (see MORE  OPENING LEADS)

Do not lead a singleton or top of a doubleton with four or more trump. Lead your long suit or partner’s suit and Make the Declarer trump. If you can force Declarer to trump two or three times then you will have more trump and be in control of the hand. Lead the singleton or doubleton if you have a high trump winner; the Ace or King of trumps. Or, if you are leading your partner’s suit.  Short suit leads are made in No Trump if you have a very weak hand with no entries and your short suit might be partner’s long suit. 

When your side has the balance of power or when no other lead is attractive: Lead Trump.  When you think that by the bidding Declarer can use Dummy’s trump for ruffing then: Lead Trump.  (This happens when Delarer shows a 
two-suiter and Dummy gives a preference.)  When each opponent bids a suit and they end up playing in a third, then Declarer might cross ruff the two suits: Lead Trump. Do not lead a singleton trump. A good trump lead is X from A X X  or K X X. (The "X" denotes a spot card.) A bad trump lead is X from Q X X.