With so much out there regarding Search Engine Optimization (SEO) it can seem to be a daunting task. Even though it goes unstated, many SEO articles are about things you can do to squeeze that extra top percent out of your site. They're the things you might need to worry about to move up from page 2 to page 1 for a given search, not the things you have to do to move from page 60 to page 1. Many of the tips you'll read about aren't the starting point, and they'll be for naught if you don't start there. If the basics aren't in place, then it doesn't make much sense to spend all your time tinkering under the hood.
Writing 'Good' Content
The wording you use is very important to determine your search rankings, but any words are usually better than no words. Don't be so paralyzed by "not being sure what to write" that you write nothing. A lot of the SEO benefits will just be a natural outcome of having the implied text on the page. If you set out to add a product description of a Waffle Iron you sell, then chances are you'll hit many of the important keywords without trying. Chances are you'd mention the brand, the model number, etc., as well as use the phrase "Waffle Iron" a few times, even if you didn't know what Google wanted to see from your page. If you don't have a predetermined set of keywords to target, simply think to yourself "what would I search if this product/page was exactly what I was looking for."
Just remember to keep the keywords you picked, and the overall goal for that page, in mind as you write your content. Where ever they come from, work in those key words and phrases often, but not so often that it reads like gibberish when you read start to finish. If you stuff so many keywords in there that it becomes gibberish, Google might sense it's being played with; but, most importantly, a person reading your page is seeing text obviously not meant for human eyes, or that reads like something that was poorly auto-translated from a foreign language, and they might leave.
SEO Isn't a Magic Trick
This is important to remember. SEO can seem very technical, and some of it is, but a majority of the job can simply be broadly summed up as "Just make your content bigger and better." More than anything else, Google loves words. The same words you and I see when we arrive at a page. Make your content better, and more relevant, for people to look at, and a lot of the SEO will probably just come along for the ride. For certain, the "under the hood" SEO is important to getting you over the hump, but it's probably not going to do the job for you if there is little content in the meaty part of the page for Google to gobble up. It's amazing how many sites I've seen where the second highest ranked page for the domain is the "About Us" page, most likely because it's the only page on their site that accidently wound up with a few paragraphs of text on it.
Real SEO Is Hard Work
The reason SEO can't be viewed as a "you're optimized or not" magic trick provided "out of the box" for you by your website designer is simple. If it was, everyone would be doing it, which would make any such tricks largely irrelevant. Google would still have to use the actual page content as a tie breaker. Actually making your site more friendly to Google and Co by adding that much content to your site is going to take time, and effort. If you want your product pages to outrank your competitors, then step one would be to write, or improve, a detailed product description, unique for each item, keeping in mind your keywords. Ideally, every page you wanted to compete would have 2-3 paragraphs of text on it, and not text that is used over and over again on other pages, with a tweak or two on each page. Likewise, copy and pasting the manufacturers default description, or even worse, stealing your competitor's descriptions, likely won't lead to getting a leg up over existing sites. Depending on the size of your website, making sure every page has unique and helpful content can be a monumental task.
Thus...SEO Is Easy
"But, you just said it was a lot of work!" I did. It is. However, for the most part, it's all work you should be doing, even if search engines didn't exist. You should have a few paragraphs uniquely describing each product because that will actually make your site more attractive to potential customers and convert hits to sales. Every page with only a couple handfuls of words on, which you spend some time being more descriptive, using keywords that a user is also going to be scanning for, will make your site better. It will help you keep people who might otherwise have left. SEO is just something you should have in mind as you add content that always should have been there. In that sense, this aspect of SEO is almost free.