There is no trick to it - you just got to remember as many as you can and note them down
Like the other guy said, don't worry about it so much. It's tough for everybody, and being stressed out just reduces your mental capacity.
The only "trick" you can use, is by not thinking of them as numbers. Remembering 4 numbers is hard, but try to replace them by things you know!
Heading 340 - Think of the airbus 340? Or think of it as NNW?
Speed 220 - Isn't that how much I paid for my speeding ticket last year?
Freq 119.5 - Hey, that's the ground frequency at airport xyz
That way, you're not remembering abstract numbers, but concepts that have meaning to you. Much easier!
But again, don't sweat it. You don't have to be amazing, just average
And this one is tough for everybody!