Whatever search engines you use make sure you follow their guidelines about the submission of sites, the kind of sites they will permit and what they recommend for optimized content. Watch for updated guidelines from Google for webmasters on likely forms of illegal search engine manipulation that is considered spam. All search engines hate spam. Google has stated in their SEO Guidelines the advice webmasters need to heed when picking a SEO.
AltaVista, Bing, Yahoo, have similar SEO Guidelines that are much on par with what Google has done.
Sometimes, even without knowing it, webmasters will inadvertently integrate techniques that might cause your site to be penalized in the site’s rankings on the search engines. If you do the proper research, like keeping track of the SEO guidelines for the aforementioned above, watch for changes, and then tweak your site to conform. If you offend you will be penalized. You must then contact the search engine that penalized your site, remove the offending material, then get back with the search engine to be back in good graces again. To avoid all this, just do not spam.
Remember to build your sites for your visitors not the search engines. To do this you need to make your site as user friendly as humanly possible by including high quality, relevant information that will help your visitors with what they are looking for and ensure a return to your site.
Your purpose, if you are in business on the net, is to convert your visitors into paying customers. You can only do this by having an easy way to navigate your site, with simple, descriptive, quality copy. Make sure all your forms and shopping carts are all working and up to speed. What will please a visitor will always please a search engine, so user friendly is the way to make your bank account grow.