Upload & Sell: Off
I normally don't chime in much around here anymore but I figured I'd offer up some information and touch on a few points in this thread..
First off, Tom, I applaud you for reaching out and offering up help to anyone who might need some direction when it comes to this stuff. SEO in general is somewhat of a grey area with very few things that are clear cut and in black and white. That being said, you have to approach SEO with a plan, not doing so will do you more harm than good a large majority of the time. There have been some good points brought up in this thread but there has also been some things you really are going to want to stay away from, and I'll try to explain why as much as possible.
First and foremost - as has been said already, content is king. Before you spend any time working on your SEO, first focus on the content of your site, and please know this is not a one time thing, this is ongoing and should always be priority number 1. All the SEO links, keywords, descriptions, etc.. will do nothing for you if your content is lacking, irrelevant or stagnant.
Page Titles & Meta Descriptions - If nothing else, spend your time optimizing here first (after content of course), it's the first two things search engines are looking at to decide what's on your page and what category you should be placed in. They should be clear, descriptive and to the point. Utilize keywords here but don't go overboard as it's not going help you, if anything, it'll hurt. Use the meta descriptions as a means to portray exactly what your site is about, and what you would want people to see in search results, as it's one of the main things Google uses in their snippets. You should write clear and description titles and descriptions for each unique page, which accurately describes the content of that page.
Keywords - You should initially only pick a few keywords to focus on, and Before you do that, you should be analyzing those keywords for their popularity and overall searches. Only pick keywords that are relevant, and actually being searched for.
Homepage SEO text - Putting blocks of text littered with keywords on your homepage specifically for SEO worked in the past, it now does very little anymore in terms of SEO and since many people try to throw as much as they can into a few sentences, it's going to do more harm than good. The main reason this has a negative effect when done this way is because it's not organic, and the search engines know this. It makes matters worse if this is the only thing on the page other than a single image or slideshow. Text on your landing/homepage should be simple and to the point, don't use keywords every other word that are bolded or in larger fonts (this does not help, <b> or <strong> tags are not viewed any differently by search engines, and haven't been for some time), only provide relevant information and links to other relevant information within your site. Remember, the search engines are looking at your site as a whole and gauging many different metrics, keep things consistent and natural throughout. The second reason this can hurt is now becoming even more important, which is experience and engagement. People don't like ugly websites, or a bad experience when they go to a site. If its bad, they leave, this is becoming a larger factor in the search engines rankings, large bounce rates and lack of engagement (people reading text, clicking links, navigating through the site etc.) is starting to play a larger role. Adding unsightly blocks of text diminishes your visitors experience and can add to these bounce rates..
Backlinks - Links are important.. BUT you need to be careful here, the very last thing you want to do is go from having 1 or 2 links to your site, to having a 100 in a short period of time, anything more than an absolute max of 10% increase in a short time frame (typically monthly) will hurt you, this is well documented. Second, the source of the link has alot to do with it's effectiveness, 1 link from CNN or similar site bears much more weight than 50 from Joe the blogger, who gets maybe 100 unique visitors a month. This also applies to the type of site is linking to you, if it's not relevant to your site, it's really not going to help you much.
Another factor that is being weighed more and more is social engagement, i.e. are people sharing your content on social media? Do those people have a trusted reputation? You should be encouraging social interaction, provide means for people to share posts/content on twitter/fb/pinterest
Repetitive content - Do not intentionally put duplicate content on pages of your site, this is bad and your search results will be punished for it. A common occurence of this is people put that same ugly SEO text they had on their homepage, throughout their site.
Now, some of you may say, hey I've done some of this stuff and it's helped! That's very possible, but you have to put that into context, if you never optimized your site before, and then suddenly started implementing keywords, descriptions and SEO text to your site, of course the search engines are going to take notice, they now have content to gauge things on. But this will only take you so far, and then you'll plateau out..
To wrap up, I want to hit back on the content topic again, focus on relevant content first, write content rich pages and blog posts which are frequently updated. This is going to help more than anything. Things are moving in such a way that all of this extra work could very well start hurting you, Matt Cutts (Google's SEO head guy) announced at SXSW that they will start penalizing for 'Over Optimization', basically in a nutshell, they are starting to compare sites and their focus on SEO, if a site is too far away from the norm, meaning they have lots more keywords, links etc than the rest of the sites, they will be penalized. In his words it's meant to level the playing field. Here is an article with the audio attached.
Some other resources worth checking out:
http://searchengineland.com/seotable - SEO Ranking factors
http://www.youtube.com/user/GoogleWebmasterHelp?feature=watch - Google's webmaster Youtube channel
http://www.markflavinblog.com/how-to-use-seo-to-ruin-your-own-online-business/ - Some SEO don'ts
http://www.nytimes.com/2011/02/13/business/13search.html?pagewanted=1&_r=1&adxnnlx=1332548192-52%20NFOAfv59vOtCtsGOQPQ - Interesting article in the NY Times about Black hat SEO