Some very good answers so far, but I wanted to add my two cents.
First, doo note that you don’t have to live in the same region that you sell. Naturally, you don’t want to live too far away from where you sell, or you’re going to be wasting a lot of time traveling (and possibly increase your risk of being ganked). However, most corners of HS have a major trade hub within (what I consider to be) a reasonable distance.
Second, do be aware that the market only shows orders within the region. So, if you’re on the edge of the region, there might be a major market hub nearby that you can’t see, simply because it’s in another region. For example, the career agent system of Hadaugago is only two jumps from Hek, but you’d never see it from the market window in Hadaugago because Hek is in a different region.
Also, you might be interested in the section, “How not to be ganker bait” from the following post.
Oh, and you can typically get more money by using standing sell orders, rather than selling to standing buy orders. However, you won’t get your money right away, and you might have to periodically update your orders because competitors undercut you. That being said, you shouldn’t have to deal with too much market competition as an explorer. As a demographic, explorers seems much more inclined to accept overpriced standing sell orders and low ball buy orders than other professions (I used to do industry and region trading, and I loved my explorer customers 
).