Search Engines read the content to varying degrees, some read up to 500 words, others less or more. So the text in the opening paragraphs is more important for cawlers. They also provide more links to crawlers. Though the target audienc for SEO is crawlers, but ALWAYS target human audience first. Any tricks to ignore human audience in favor of search engine crawlers is going to prove futile both in short and long term. Not only such practice drives your customers away, but also in long term Search Engine crawlers will immiate more human behavior and discover your tricks.

With that said, there are many legitimate ways to cater to non-human audience with no net negative effects on humans. Some tips discussed in this article maybe suitable for human audience as well.

Spin your story around keywords, and make it comelling to humans simultaneously. Using keywords in the opening sentences help gaining attention of human readers as well. Experiment with keywords to determine what suits your needs. This takes into consideration both demand and supply side. You may want to start with demand side by researching the keywords people are using to find information in the domain you are. And once you have experiment with top demand keywords, look at supply side to determine what works well. Supply side is you. People on web may be searching for tons of things, but you as a publisher might be good at only few of them. You can discover your strenghts by analyzing search terms people are using to reach you.

So, this is an iterative experimental process. You start with the top keywords that you think are profitable as well as matches with your offering. But then you take into consideration vote of your audience. You refine it and refine it until you reach a point that you and audience are on the same page. You have a set of keywords that are profitable to you and your audience think you are the right publisher for them to go to for those keywords.

"Forget Generic, Get Specific"- is another lesson in organizing content for keywords. Refer to my another article-Keywords to Target in Search Advertising for more details. You can get significantly better results by targetting specific keywords.
One would have carefully craft the content which has the right keywords, and the keywords are specific enough. Highlight the keyphrases in different ways, use them in heading, title and in starting of paragraphs.

You should continuously research on why people come to your site, and scope the site accordingly. Don't fall into temptations of including "dog food" on "accessories site", just because you think people "might" be interested. Keeping the site focussed will improve the quality of visitors and SEO ranking over time.

Finally, don't ever try to trick the search engines. Using invisible text on web page can get your site banned for months. Search engines are continuously improving their algorithms to update indexing with new cheating techniques people deploy on web.