When playing cribbage, many players focus on preparing the best possible hand for the show, or part of the game where the players count up the values in their hands, and many overlook the significance of scoring well during the play, or initial part of each hand where players play cards one after another and peg when one hits a significant point (15, 31, pairs, runs, etc.) or scores a go. Scoring well during the play can end a game early, and many a weak show hand can be compensated for by developing one's skills during the play. Because this phase comes first in every hand, games that are close at the end may come down simply to which player can peg the most during the play, and therefore this often-overlooked part of the game can be the difference between a win and a loss.
How to Score
The first way to score during the play is by playing cards that add up to 15 (i.e., if your opponent plays a 6, you play a 9). A 15 is worth two points. Two points are also awarded for reaching 31. If neither player is capable of getting to 31, the last player to be able to play a card will be awarded a "go," worth one point. Pairs are worth two points, with three of a kind (a "pair royal") being worth 6 points and the elusive 4 of a kind (the "double pair royal") worth 12 points. Runs are worth a number of points equal to the number of cards in the run (i.e., a run of 6-7-8-9 is worth 4), and, theoretically, a run of up to seven is possible (A-2-3-4-5-6-7), though it is rarely seen.
Trick your opponent
Sometimes, the best move you can make during the play is the one that prevents your opponent from scoring or the one that tricks your opponent into allowing you to peg more points. Many cribbage guides suggest leading with a card of a value lower than 4, so that you are more likely to be the one to get to 15. If you have a 6-7 in your hand, you may want to lead with the seven, tempting your opponent to play an 8 for 15 (two points). You can then play the 6, giving you a run (3 points), although your opponent could just as easily counter with a 9, giving him a run as well (4 points) and, unless you have an ace, the point for last card as well.
Your opponent is probably tricky too
Always keep in mind that your opponent is very likely baiting you as well. Be wary of taking every 15 offered, as it is likely to be countered with a pair or run. Scoring with a pair may be your opponent's way of luring you so that they can get a pair royal. As with any other game of strategy, you will have to watch your opponent and learn the tricks and habits that they have while they play-- it will not only make you a stronger player, but it will give you the edge that you need to win.