When flying an instrument approach in a test, you’ll know ahead of time which approach is to be flown and can prepare on the ground. In real life, you may not be able to prepare in advance, so know your way around the plate so that you can extract essential information quickly.
Some pilots use unwieldy and generally unmemorable acronyms to brief the approach. I find that a flow, or visual scan, around the plate is a better way to self-brief. You can use a pen on the plate to highlight key information. The only elements requiring any maths are the approx. descent rate which varies with ground speed, and the all-important minima.
Presentations vary, but here is a ‘flow’ that works for the UK AIP plates.