Source: www.rpbridge.net
Declarer’s goal in the great majority of suit contracts is to maintain trump control, the ability to draw the enemy small trumps and enjoy his winners in the side suits. This task is usually easy with nine or more trumps. It is the contracts with eight trumps that frequently cause trouble.
This lesson explains the important trump-handling techniques and the ways to cope when the opponents try to shorten your trumps.
Ducking the First Trump
Whoever holds the ace of trumps has great control over the play. If on lead, two rounds of trumps can be led at any time; and if not on lead, the lead can be obtained whenever a trump is led. As declarer it is often wise not to release this card.
[box]If you have the ace of trumps (without the king) and expect to lose two trump tricks, it is usually best to duck the first round.[/box]
1. 4
South
Your trump suit is flimsy but the contract is sound. You would like to play exactly two rounds of trumps, after which you will ruff dummy’s two low hearts. All you need is a 3-2 trump break provided you take advantage of the A to control the play.
Win the 
K and duck a spade (key play). Whatever the return you will next cash the A and go about your ruffing. The only outstanding trump will be a high one, so it makes no difference if or when an opponent ruffs.
Rejecting a Finesse
When declarer’s trump suit has an internal loser (typically the queen), the best strategy is usually to draw two rounds of trumps to leave an opponent with the high trump and let him ruff as he pleases. Unfortunately declarer is often lured into taking a losing trump finesse, after which it is necessary to draw three rounds of trumps or risk leaving an opponent with a small trump.
[box]If your contract is safe with a 3-2 trump break, do not finesse for the trump queen if its loss would jeopardize the contract. Be sure to understand that this applies only if you can afford to lose a trump trick. If not, a finesse is correct with eight cards missing the queen.[/box]
2. 4 South
Assuming a trump loser you have nine top tricks and the heart suit offers the only chance for 10. Unless the hearts break 3-3 (unlikely) you must ruff the 3 in dummy after drawing two rounds of trumps. If you take the losing trump finesse, you will fail because West will have a small trump to ruff the third round of hearts.
The solution is to reject the trump finesse. Simply cash the A-K then lead hearts — the only ruff West can make is with his natural trump trick.
Essentially, it’s a matter of choosing to rely on a 3-2 break (68 percent) instead of a finesse (50 percent), an edge that will show a big profit in the long run.
Drawing the High Trump
In most cases you do not need to lead trumps when a single opponent holds the high trump (or trumps) — you just lead your side suits and let him ruff when he pleases. An exception occurs when one hand (usually the dummy) has a long side suit and no outside entry, in which case an untimely ruff would shut out the long suit forever.
[box]If you need to run a long suit without interruption by a ruff, lead trumps to force an opponent to win the high trump.[/box]
3. 4 South
After winning the K you routinely cash the A-K. The temptation now is to run the hearts hoping to discard clubs; but West will ruff as you discard your first club, after which dummy will be left high and dry. You would not enjoy the ending; the opponents would exit in clubs forcing you to ruff, and you would have to lead diamonds from your hand — down one.
The solution is simple once you think of it. Just lead a third trump to West before running the hearts so he is unable to ruff in. The opponents can take their club tricks (else lose them altogether), but you will win the rest. Note that you do not even need the diamond finesse.
Delay Drawing Trumps
Declarer’s most difficult task in maintaining trump control occurs when the defenders shorten his trumps by making him ruff early in the play. This is called a “forcing defense” and it can be deadly if declarer is not careful.
An effective countermeasure to a forcing defense is to delay drawing trumps. The purpose is to keep at least one trump in each hand, then if one hand is exhausted of trumps, the opposite hand can take over to maintain control.
[box]If the opponents make you ruff early in a 5-3 trump fit, it is usually necessary to delay drawing the third round of trumps.[/box]
4. 4 South
The opponents begin with two rounds of hearts forcing you to ruff. You lead a spade to dummy’s king then a spade back to your 10 as West wins the ace. Another heart forces you to ruff again, leaving you with one trump in each hand. If you draw the last trump now, your contract is history — as soon as East wins the 
K, the opponents will cash two heart tricks.
You must leave West with his trump and take the club finesse: Low to the queen is best to diminish the chance of a holdup — if you led the jack, a cagey East player would duck the first and win the second round to give West a ruff.
You can handle whatever East returns. If he leads a heart, you can ruff in one hand and cross to the other hand in diamonds to draw West’s last trump.
Discarding a Loser
Another technique to avoid shortening your trumps is to refuse to ruff — sometimes you will have a sure loser to discard instead. If the opponents persist with the forcing defense, you may be able to take the ruff in the opposite hand.
Unfortunately this tactic is often misapplied. Situations of this kind are tenuous; declarer must weigh the consequences of ruffing versus discarding on a case by case basis. A word of caution:
[box]Before discarding a loser instead of ruffing, check that you will not be worsening the situation. Ask yourself, “What can they lead next?”[/box]
5. 4 South
You ruff the second heart lead and win the A and K to discover the annoying 4-1 break. Note the technique of leaving the trump suit flexible (J opposite Q-10) with only high trumps remaining. Do not lead any more trumps in order to keep a trump in dummy. Lead the 
9 and let it ride to East’s queen, and assume East returns another heart.
If you ruff you will have fewer trumps than West, and the hand will collapse. Instead throw off a club. Since dummy now is also out of hearts, there is no return that will hurt you and you can easily win the rest of the tricks.
Note the importance of taking the first-round diamond finesse — if you cashed the ace or king first, East could defeat you by giving West a diamond ruff.
Regaining Control
In some cases it is inevitable that the enemy will shorten your trumps so that one opponent holds more trumps than you do. You still might survive with careful play. Do not overlook the possibility of changing your line of play to a crossruff — often you can scramble home with enough tricks in spite of the forcing defense.
If a crossruff will not work, your only hope is to regain trump control by forcing the opponent to ruff — try to shorten his trumps just as he has shortened yours.
6. 4 South
You ruff the second heart lead, cash the A-K, then lead a diamond. West wins the A on the second round as East sheds a club. If West gives East a diamond ruff (bad defense), you will have no problem so assume West returns a third heart and you ruff. It would be a mistake to discard on the third heart as a fourth heart would cripple your trump holding (a ruff in either hand is fatal) or East could ruff a diamond.
At this point you have one high spade in each hand and East has two spades. Do not lead your trump. Lead the good diamonds until East ruffs, after which you can draw his last trump and make your contract.