I'm developing a Rails site for my company that's going to be a web store for our entire inventory. I don't really have a lot of experience with design (I am the one-man IT department at my company, so anything remotely computer-related gets thrown my way with the assumption that I am magical and capable of anything), so I was wondering if there were any more or less omnipresent elements in the designs of most modern e-commerce sites. Are there any near-universal guidelines for how an e-commerce site is expected to look / be designed?
A good method, I find, is to go to a few people who are used to using the internet and buying things off of it.
Ask them some questions like: "You want to make a search on a website, where do you look?" and "If you want to find out a phone number for the site, where do you look?" (the answers to these tend to be "top left" and "in the footer", in my experience). Also, as Mateus has said, don't go over the top in functionality. It's a lot easier to find the thing you need when there's less on a page.
In other words, stick to convention. I believe this has drawbacks (see this blog post of mine on the subject, if you like) but for now it's certainly the best way of doing things.
I have two good bookmarks on delicious you really have to check out http://www.delicious.com/mateusnroll/ecommerce
But, just remember: BE SIMPLE. Don't clutter the interface with all kind with elements. I recommend everyone that's starting to read Save The Pixel book. It have good insights.