"Over Optimization" is referring to the new Google Penguin update. The main thing that you need to do is ensure that you are not using an black hat techniques on your site such as keyword stuffing, hiding text, or writing content that is just filled with useless links and keywords. If you follow the webmaster guidelines that have been in place for the last few years, you should not run into any problems. Good luck.

For those who have not heard about Over Optimization please Google Over Optimization Penalty and you will find your answer.

To keep your website safe from Over Optimization Penalty make sure your website has unique content and it is not using the keywords in excess. Keyword density should not be more than 3% in any case. Make sure your website's title and descriptions looks natural. They should not looks like someone has written them to increase website rankings.

I don't think there's anything like "over optimization". The more optimized your website is, the more it'll rank in search engines.

It depends upon how u optimize you site for your keywords in onpage and offpage both or in any one of them, If you have done bulk submission for given Keyword that it comes in Over optimization as well as if you use Key Stuffing, high density of keyword then it also the over optimization, so keep in mind to use keyword according to search engine guidelines, Make and use ur site for user not for search engines.

Make Quality theme based links for you website that will boost you traffic as well as ranking.

Please define "over optimization". Never heard of the phrase or the concept implied by the phrase.