Doing your homework will give you the best possible chance to save one. As an amateur player this might be difficult, but if you can watch your opponents striking a ball that would be a massive help.
When it actually comes down to facing a penalty, I try to wait as long as possible before deciding which way to go.
I watch the player’s run-up, eyes and body shape, then make a quick decision on which way to dive. It all happens very quickly so you have to be positive and committed.
By waiting as long as possible to decide, you make it more difficult for the penalty taker. If you dive early, you make up the taker’s mind.
More than anything, you have to believe you’re going to save it. Stay calm and stick to your plan. If you start hesitating and questioning yourself, you lose the initiative.