Quick example of line of site/elevation is king:
I've been working a local contest that is metroparks on the air. Saturday I was at one parking lot that I thought was pretty high, elevation 971. I got one contact, report was that I was extremely scratchy at 50W, so I went to another parking lot, elevation 990, and picked up 4 contacts immediately. Inversely, I went to the next park, which happened to be in the valley right next to the Cuyahoga River, and managed a single contact that I know lives in the valley 5 miles away, but couldn't get a friend only 3 miles away at the top of the hill.