I said "I browse randomly," but that's not entirely true. I notice recommendations and collect freebies, but they often don't lead to sales or even reading. I tend to browse with a specific goal in mind--"I'm looking for something light and funny" or "want something currently political with a side of philosophy" or "bring on the pr0n!... as long as it's less than $4."
I browse Smashwords with covers turned off because (1) I browse at work and (2) most of the covers are *atrocious* and are more likely to turn me away from something I'd like than draw me in.
I tend to skip around and try lots of different filters. It drives me crazy (by which I mean, "prevents me from buying ebooks") that they're all sorted by most-recent-update; there's no filter by price (other than "show me the free ones"), no filter longest-to-shortest or vice versa, no way to combine keyword searches with categories (or at least, not that I've found; if there's a way to look for Pagan *nonfiction* only, I'd love to know what it is). So I consider Smashwords browsing kind of like poking through a rummage sale; lots of cool stuff, ten heaps more junk, and just take some time to look at things and maybe find something I'd like. There's no way to sort by tag+keyword, or genre+tag, so it's all rather haphazard.
Fictionwise browsing is easier (they'll sort by price or length), but still doesn't allow tag/keyword searches. However, the ability to find other books by that publisher tends to get things in a similar range. I understand why Smashwords can't do this (well, they can, but with so many individual authors it's just not useful), but it'd be nice to see ways of grouping books other than just by subgenre.
I read a swarm of publishing blogs, and get notes about freebies from some of those. I get recommendations here. I get occasional suggestions from fanfic writers & readers.
I keep thinking I should find something more systematic, but ... I'm not running out of things to read.