Well, since I've only recently been enlightened on the Ni and Fe that is prevalent in myself, and I hadn't really understood my supposedly primary processes very well, I'm pretty hesitant at this point to start talking about Se!!! I doubt I really understand what it entails either!!
But, just based on your post, if you're talking about external details/objects in our surroundings, I actually think I'm pretty aware of them.
I'll have to back up to my childhood. One of the things I became very interested in when I was about 10 was birdwatching. I think the act of birding is an Se activity. You're constantly scanning your surroundings for bird movement - amidst all kinds of other moving things - leaves fluttering, squirrels rustling, etc. So it's a totally sensory activity. Now there are other skills that come into it too, but the *act* of birding is Se, I think. I would assume Si is the memorizing of plumage details and vocalizations?? There's also a lot of pattern association and distribution associated with it, which come into play when you're debating the liklihood of a particular bird being somewhere, habitat, etc - which is perhaps Ni or something like that, with Si too. ANYHOW.
I'm thinking all of my time outdoors, and my love of those details, probably heightened my Se. From birds, I grew interested in flowers, and then I started noticing all sorts of other details while I was out -- and now I find myself even noticing insects and fungi and moss growing on trees...
Also, I may be more Se-oriented because I was pretty solitary/alone growing up, and most of my teenage years, when I wasn't doing something extracurricular, were spent in thought or observation. Since I was super self conscious and didn't have many friends to speak of, I spent most of my time just observing. Watching everyone around me. Maybe I picked up on it then too.
As for developing it? Well, maybe you could just make it a point to develop it, you know??

Just consciously take yourself out of your inner world for a bit, blink your eyes, and really look at everything around you, and focus on what's around you. Take it in. Maybe do that for 5 minutes. Maybe that's a start. And I'm sure there's some sort of hobby/sport you could pick up that could exercise your Se a bit more. I do climbing now, too, which is pretty sensory.