I'll go head and put it in layman's terms: set your shortcut button to ISO setting, dial in the M mode, and then play around using the exposure meter(the meter stick bar you see in the viewfinder that fills to the left or right unless you hit that next-to-golden middle) until you get a hang of how ISO, shitter speed, and aperture come together in taking pictures.
Towards the left is over-exposure aka lighter pics than that supposed golden middle. Towards the right are under-exposed shots that yield less light but more shadows and details. Past that, play around and see what looks best to you. And remember that you can always photoshop anything after you take it to dial it in.
Things like clouds work better slightly under-exposed so you can actually see them later on.