Often people who only know a little about SEO have a go and get it wrong; they make look for a quick fix and get sucked into some black hat techniques. This though can be serious if you use SEO techniques frowned upon by Google and other search engines. If this is you or you have been asked to help out someone with a website where their previous SEO company have used dodgy SEO techniques how to get off of any blacklists is the first thing you need to think about.
Firstly make sure you are signed up to Google Webmaster tools for the site in question, Google will tell you if something is wrong and if you get the message and act fast you can sometimes stop any action being taken.
If though the messages coming through from Google are saying that they have identified you using SEO techniques they don’t approve of, such as link schemes, you may have a steep hill to climb.
If this has happened you will probably have seen most or even all of your organic traffic disappear that could be worth thousands to you. You can have your site reconsidered though once you have changed your SEO techniques. Firstly of course remove the offending links, this includes ones from your site to others that may be in a link scheme and also those coming to your site that may be more difficult.
If you have used any other SEO techniques that Google may see as Black Hat such as in your on page optimisation change these back as well. Now resubmit your website to Google, if you couldn’t remove some links or have links that you feel they wrongly identified then tell them about it and explain.
If you are objecting and claiming that you did nothing wrong though be careful and be ready to back it up with some evidence: if you can’t though it may seem unfair you may have to remove links that you think are genuine. Also don’t try and argue that the techniques you used should be allowable if Google have plainly stated in the past and SEO best practice is that these SEO techniques are not acceptable.
Google will work with you if you show willing but can get fed up with you if you try to argue with them and leave you out to rot if they wish.
Of course if most of your links are from link schemes that Google disapprove of you may find you have to start your link building again and this is just the way of it; you could in such a case though be tempted to start again with a fresh new site and no history that Google may remain aware of even after your penalty has expired.
Even after reconsideration it could take 30, 60 or 90 days for your rankings to be restored as Google sees fit. To minimize the penalty that Google decide to give you after reconsideration you could use some SEO techniques that they wholly do approve of such as good quality fresh content that may show them your site’s value for searchers.