Definition

The opening lead is card first played after the contractThe final suit and level of bidding sets the number of tricks and the trump suit for the game.This is called the contract. The partnership that wins the bidding can earn the points if they succeed in getting the number of tricks they contracted.
The number ... has been bid. The player sitting to the left  of the declarerThe player who during the auction made the first bid the SUIT of the final contract, becomes the declarer.  The also play their partners hand which  is now renamed 'dummy.'
Declarer plays both their own and dummy's hand. is the one who has the responsibility of choosing both the correct suit and the correct card in that suit. The purpose of opening lead ‘suggestions’ are to help defenders mount the strongest possible attack on the contract of  declarer.

Opening Lead Suggestions

Your opening lead decision differs depending on whether the final contract is in No TrumpsA suit of cards with the highest ranking over the other suits in a particular hand
Noun usage - A card in the trump suit whose trick-taking power is greater than any other suit card.
Verb usage - To play a trump after a plain suit has been led or otherwi... or in a suit. Review the auction and try to avoid leading a  suit that the opposition have bid as you may be giving them a ‘free’ trickA round of 4 cards where each player contributes 1 card. There are 13 tricks in a game of bridge.. It is considered very good form to lead partner’s suit if they have bid one.

General Principles for Opening Leads

• lead low from three rags with a single honorSometimes known as face cards or honours , each is worth high card points. They are:
  the Ace (A)  = 4 HCP
  the King (K) = 3 HCP
  the Queen (Q) = 2 HCP
  the Jack (J) = 1 HCP
  and the Ten (10 or T) in each suit
  The 10 and 9 card in any suit are k... (Q or J )
• lead the middle from three small cards; (known as MUD playing cards in order of middle – up – down) 
lead the suit that is strongOpeners strong hand contains 17+ points Responders strong hand contains 16+ points In NoTrump its high card points In a suit its total points (with distribution points) for the next player towards weakness in the last person to play
lead suits that the player biddingThis term is also called the 'auction.' In each online deal, a player is the nominated as the dealer -this title rotates each new game. The dealer is the player who starts the bidding even if its a pass. Players take their turn at bidding in turn and in order ... after you has bid – where they have strength, if there are weaknesses in their suit maybe your partner can win with a low honor cardAn honor card is sometimes referred to as a face cards
the Ace (A)
the King (K)
the Queen (Q)
the Jack (J)
and the Ten (10 or T) in each suit
The 10 and 9 card in any suit are known as Intermediate Cards
lead trumps if any other other suit leads will help declare get a ruffAnother word for trump a way to win a trick and it means to play a trump card on a trick when that player has run out of the suit which was led. If trumps were the suit led then following suit and playing a trump card is not 'ruffing' its following suit and discard
don’t lead away (by leading a low card) when you have an Ace or King sometimes its unavoidable but try not to 
do lead unbid major suits – especially if the opposition are in a minor suitDiamonds and the club suit are the minor suits, often referred to as 'the minors' contract.
do lead to remove declarer’s entries (high cards) from dummyThe declarer's partner is called the dummy, and after the opening lead has been made by the opposition dummy lays all their cards on the table face up.
That is the end of this game for dummy and they have no more to play in this game.
Declarer now plays ....
lead the suits that dummy bid to get them won before declarer cross trumps

Leading to the Second Trick

Once the opening lead has been made and dummy has been tabled, both of the defenders will have more information. When your partner has led, the first question you should ask is, “What does partner’s lead tell me?” If you have won the first trick, you must decide whether to return partner’s lead or change suits.