It is crucial to, if possible, defeat your opponnent as quickly as possible because many match play tournaments are contested over numerous rounds and can be very tiring, physically and mentally. In the US Amateur, for example, the finalists will play ten rounds (including two practice rounds) during the week.
My personal rule, taught to me by a wily old Irish golf professional, is to never give a birdie putt or a putt for a win, regardless of the length.
I talk with my opponents on the first tee and let them know this so that they do not assume any putt is good. ( Also, I expect to have to make every putt, so as to always be prepared to have to.)
There are exceptions, of course. This past summer, I was in a tight match in the quarters and made a blubbering six on the par four eighth. My opponent was on in two, but sixty feet away with a steep uphill putt.
Had he lagged close I probably would have conceded the hole. However, his first putt came up to the Crest of the hole and went back to its original position. ( Think Stewart at Olympic.)
As I assessed the situation, I realized that the hole was cut in a rediculous place, a fact confirmed when the tournament director stepped near to me and said "I think I goofed on this one." Just then my opponent's next putt did exactly what it did on his first one. Now I was stuck, I couldn't concede the hole. But after his next try I gave him his putt for the tie. I couldn't give him the hole, but no way was I going to let him lose it, under the circumstances. (I won the match in 21 holes.)
Turns out the players in the match behind us both hit the green in two near to where my opponent's ball had been, surveyed the hole location, and agreed on a half. The hole was then relocated four feet farther back, which solved the problem for subsequent matches.