When you're out scouting a landscape for potential paintings, it's crucial to stop and look at the scene in sections, to remember that you don't have to include everything. To this end, it's helpful to take a viewfinder (or use your fingers as a viewfinder) to help isolate part of the scene. Trying to include too much in a painting (and especially on a relatively small canvas) can mean you end up with a work that lacks focus, and seems cluttered.
The stretch of coastline shown in the photo (above, bottom) is one I've walked along regularly. But then one day, after I'd been reading a monograph on Monet, paying particular attention to reproductions of some of his seascapes (such as this one in the Musée d'Orsay), I suddenly noticed the strong curve of the cliff edge, which echoes the curves of the hills in the distance.
Cropping the scene to just a section (top photo) makes for a strong composition, dominated by curves contrasted by the horizon line. I've sat on the benches admiring the view there many times, and I've done paintings featuring the hills in the distance (see this painting demo), but I'd never considered the cliff edge at my feet until before. I'd been looking at everything, including too much of the view, rather than considering smaller aspects of it. Inspired by Monet, I saw the piece of coastline with new eyes, and will never see it the same again.