Your team is trailing late in the game; if you don't score some runs now, the game is over. Some players - indeed, some teams - seem to shine in these situations, and have a tendency to come through in the clutch. Here are some tips to help your team become one of those opponents that no one can count out.
Don't hype the situation. Resist the urge to explain to your hitters how important the coming at-bats are. Tense players perform worse than relaxed ones. Don't worry about the score, and don't let your players worry abot it. Get them to take a deep breath, to relax, to treat this like any batting practice. After all, the mechanics of a clutch batting situation are no different than those of any other plate appearance.
Be ready. If the opposing pitcher smells blood in the water - in other words, if he has a lead late in the game - he's going to come right at your hitters. He'll try to throw strikes early in the count, then retire them on junk out of the zone. Your hitters need to be ready to hit as soon as they step up to the plate; the first pitch or two they see are quite likely to be the best ones in the entire at bat.
Make the pitcher throw strikes. While your hitters do need to look for early strikes, they can't get over anxious. The pitcher may be suffering from butterflies himself in this clutch situation, or he may be tiring. A walk is as good as a hit, as it puts a runner on base, representing a potential run. Furthermore, it gives the pitcher something else to concern himself with, and increases the chance of a mistake on the pitcher's part. Don't let good pitches go by, but don't chase junk.
Swing for a base hit, not a home run. It is terribly tempting for a hitter (especially, for a good hitter) to get caught up in the situation and try to launch a home run. Instead, emphasize that uut of control swings hurt the team. You need runs right now, and the best way to get those are by getting men on base. Solid line drives are the goal in a clutch at bat. Don't try to pull the ball, don't try to crush it, don't try to hit it high - use the entire field, and simply put the ball in play with solid contact.
Use your head. In pressure situations, pitchers tend to fall into a rhythm. They throw the pitches they are most comfortable with, and throw to the spots they are most able to hit. Use this knowledge to your advantage!
Before you ever get into "close and late" or "rally" situations, you should teach your team the correct mental approach. Clutch situations are truly the time to shine; look forward to them, and have your players do the same. If they know how to handle themselves, your chances of winning improve dramatically.