Question: Every time I go walking or hiking, I generally spend most of my time looking down to make sure I don't step on a snake or hole or dog poop. I don't do it consciously, it just happens. Obviously, I miss out on a lot of birds and small animals up in the trees and I'd like to see how other people cope with the urge to avoid obstacles and just enjoy their surroundings.

How can I go walking and hiking without constantly looking down?

Answer: 
This may seem kind of obvious, but I use a scanning technique. I like to look at the next 10-20 feet, look up on all sides, look down, and then look up. It's a lot like driving, scan your mirrors, then your environment, then your dash or whatever you need to, and then repeat. It does take mental purpose, so you will have to train yourself. 

I like to scan ahead, look up at one area, say my right, scan, and then look to the left. Mostly it is second nature.
Ha ha. You can't. At least not off a leveled surface. I've struggled with this too. If I look down I miss the views; if I look up I trip. So I look ahead for a place to stop and enjoy. Then I march on, eyes on the rocks and detritus in the trail, until I reach my looky place.