Found this… by Hoyle ??
Cribbage pegging
The count
In the next phase of cribbage, the players take it in turns to lay down a card, trying to make the running total equal to certain values. The non-dealer plays first and states the value of her card (for example, “ten” for a Jack). Court cards count ten (together with the face 10 they are known as the ‘ten-cards’, or ‘tenth cards’). Ace counts one.
15 and 31
The dealer then plays a card, the value of which is added to the current running total. The player who makes the total exactly 15 scores two points (“fifteen-two”). Two points are also awarded for making 31. Additionally, you score a point if your opponent cannot play without going over 31 (“one for the go”, or just “one for go”).
Pairs
If your card is the same rank as the last card played, you score two for a pair. If your opponent plays a third card of the same rank, he scores 6 for a “pair royal” (three of a kind). Four of a kind scores 12 (“double pair royal”).
Runs
If the last 3 cards played form a sequence, the player making the sequence scores 3 for a “run”. For example, 3-4-5 makes a run of 3 and so scores 3 for the player laying down the 5. If the opponent then plays a 6 (or a 2) to extend the sequence to 4 cards, she scores 4, and so on as long as the sequence is unbroken.
Sequence do not have to be in order. For example, if the play goes 7-9-6, you can then play an 8 to score 4 for a run of 4.
The rules of ‘go’
The cribbage rules for scoring ‘go’ sometimes cause confusion. You earn a point for go when your opponent cannot go. This may be (a) because he has no cards (sometimes called ‘One for last’), or (b) because he cannot play without going over 31 (‘One for the go’). In either case if you make the total 31 you score only 2 points on the cribbage board, not 3 (because the go is included, as described above). However, you may well make 15 with the last card (in which case you do score 3).
This is exactly how I have played for over 30 years…
big G 
I also have played with people who take mulligans, any points you missed counting in your hand or your crib, they take. 
