This page assumes you are familiar with the correct usage of title, alt and heading tags. If you're not go one step back to How unhelpful code affects your SEO.
Those who scam have become masters at trying to game search engines and lead the likes of Google to refine what they will and won't accept to ever greater degrees of accuracy. The downside is that some innocent webmasters get caught up in the net so it is important to understand how and why your website could be thrown out of the Search Results.
There is outright scamming - if your website is about selling a book 'How to be successful' but your meta tags and title contain words like "Princess Diana" or "Free money" then alarm bells are going to start ringing with the search engines. Titles and meta tags that don't match the content are, to them, a sure sign of scamming.
In the same vein placing misleading keywords in the alt tags of your images will also land you in hot water.
But where some DIY SEOers come unstuck is not that they are actually trying to scam, but because their titles, subheadings and alt tages are not descriptive enough and they get mistaken for scamming.
Part of SEO is to accurately match your content to your title, meta, heading and image tags so search engines feel confident that your page is relevant to a particular topic and you don't become an accidental victim.
The key is to be descriptive and think of the user first. For example:
There are many websites that are solely made up of other people's content. This is often carried out in a totally legal fashion by taking RSS feeds from someone else and placing the data on their own website.
The motivation for copying is that the content is free and there is lots of it available which means making a text rich website with little effort is easy.
Absolutely nothing wrong with this but as search engines get faster and faster they also get better and better and finding the original source first and discounting those who copying it. This means they will display the orginal first and the website that is copying .... well probably not at all as it adds no value to the search. SEO will not be able to help a website like this.
There are however two ways in which copying does not affect, and may even raise, your rankings:
Mixing - you might mix several RSS feeds together to give, for example, "Reviews of Uncle Jack's Orange Juice" which contains reviews taken from several other websites.
Now you are copying but you are also creating genuinely useful information as you are providing original content by mixing a number of pieces of data together which can add value. This makes it unique and SEO can help promote it.
Matching - is a similar method where you create code, or manually intervene, to make sure the copied information is relevant to your readers. Let's say you own a website selling outboard motors for boats and you get a number of RSS feeds from different publications but you only display those that contain the word "outboard motor".
You are copying 'outboard motor' stories from websites or publications like Yacht Weekly and Go Sailing Monthly but only selected stories with a particular theme. As long as there are not too many people doing the same type of copying the search engines will conclude this 'filtered' copying might be useful to someone and they'll be looking for user behaviour signals to confirm this.
The you may go further to remove certain stories that won't be of help to your users such as the story "Man killed by outboard motor"(!). Your 'Outboard motor news' page is copying but copying selected theme related content from a number of sources and if users respond positively to it, so will search engines.
Copying also is not copying if you are changing the format. If, for example, you take someone's dull block of text and change it into an easy to digest infographic or video then theoretically it is the same information (it is copied) but search engines don't recognise it as such and internet users may appreciate it.
Copying isn't as evil as some paint it so long as it is done with care and creates value to a group of internet users.
I'm Tim Hill, a Search Engine Optimisation and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.