This is a piece of advice about which seo companies you should fear, part of How to Chose an SEO company?
Fear companies who tells you you can be inside 15421254 directories in one second. First, it's a lie, and then this would hurt your ranking. Google is not stupid!
Escape from those who want to throw 154215445 times the same word in your 20 pages website. Google, baidu, yahoo, all use statistics to check that you are not over using a word.
Hide from those who promise you to be first on hotel, after 1 week (because they are lying). There are very competitive keywords, and their for you have to use a strategy, not pay voodoo master.
Do not follow those who will promise you 1000 relevant backlink in a night (they use spamming robots). They attack for example blogs without captcha. Again, search engines are not stupid (and the engineers who design them as well).
Be careful of those you pay according to the traffic growth (because they can buy ads who will disapear as soon as you stop paying them, with the traffic they were bringing)
Don't copy, google knows it better than you're teachers used too (and if your teachers were good at finding out, imagine what google can do)
to sum up, "don't be evil", bring valuable information, optimize your website so that you put the right words at the right place. always think as a user. if "i type your page title, and i find it, will it be valuable information for me") search engine optimization is not about tricking, it's about serving...serve your readers and serve search engines, they will serve you