It's inevitable that the day will come.
Your regular keeper is out injured/hung over/unavailable. Despite the captain desperately searching for a replacement, none can be found.
Straws are drawn and someone gets the short one.
A pair of gloves are located and shoved on the mitts of the unsuspecting batsman (it's always a batsman).
What are the 3 most important things to remember through the panic and fear?
You have no time to work on technique (although it does help to have a basic understanding of catching with gloves on). That leaves the tactical side:
1. Keep concentrating
A decent catcher will do OK as a stand-in keeper, but the tricky part (even for regular keepers) is when the fatigue sets in.
It's hard work to concentrate on every ball with intense focus, especially when combined with crouching and getting up to add to the physical effort. It can be a culture-shock to a part-timer.
That's why the stand-in has to quickly develop a way of 'saving' focus by switching off between balls like you do when you are batting.
2. Get there
Nobody expects a technical masterclass on wicketkeeping, but it's important to get to as many balls as possible.
That is as much about attitude as it is skill.
The keeper who is prepared to throw himself in the dust (or mud) to turn 4 byes into 1 or prevent overthrows is doing a superb job. It's risking teeth and fingers in the process and is a thankless task.
It's said the best wicketkeepers are silky and hardly noticed. The stand-in can be ugly and ungainly but at least he or she is there and taking a bullet for the good of the team.
And in an emergency situation, that's more important than the ball melting into the gloves.
3. Ignore the mistakes
Mistakes are inevitable. If full-time Test keepers make them, your last minute keeper with borrowed gloves is bound to.
The reaction of the team and the keeper is very important. If everyone decides to put the mistake out of their mind then the chance of it happening again is reduced.
So the rest of the team need to be supportive when mistakes happen and the keeper needs to 'clean the slate' and get back to catching the ball again.
Some people are naturally more inclined to let mistakes get to them. You can train yourself to overcome this, but the stand-in hasn't got time for that.
It may be that when picking the stand-in you go for someone with the ability to keep going even when a catch is dropped.
And that's the secret of becoming a good wicketkeeper fast: You need a certain mental make-up.
Be prepared to throw yourself around in the dirt, give your all, put mistakes out of your mind and deal with the relentless pressure of trying to catch every ball.
And finally, hope the real keeper is back for the next game. You have to be mad to do it full-time!