How To Contribute To Wikipedia!

It's very unlikely that a frequent internet user had never stumbled into Wikipedia. Its an idea which has accelerated & revolutionized the information sharing between people. It's very much similar to Open Source movement & many times it's being related to it.

Wikipedia gets priority in Google search due to its huge user base & bulk of information. Almost every type of information exists in Wikipedia.
Wikipedia pages are created by the huge contribution of volunteers who shared their information.
These are the excerpts from About Wikipedia which explains the working of Wikipedia.

Wikipedia is written collaboratively by largely anonymous Internet volunteers who write without pay. Anyone with Internet access can write and make changes to Wikipedia articles (except in certain cases where editing is restricted to prevent disruption and/or vandalism). Users can contribute anonymously, under a pseudonym, or with their real identity, if they choose, though the latter is discouraged for safety reasons. The Wikipedia community has developed many policies and guidelines to improve the encyclopedia, however, it is not a formal requirement to be familiar with them before contributing. Since its creation in 2001, Wikipedia has grown rapidly into one of the largest reference web sites, attracting nearly 68 million visitors monthly as of January 2010. There are more than 91,000 active contributors working on more than 15,000,000 articles in more than 270 languages. As of today, there are 3,262,891 articles in English. Every day, hundreds of thousands of visitors from around the world collectively make tens of thousands of edits and create thousands of new articles to augment the knowledge held by the Wikipedia encyclopedia. (See also: Wikipedia:Statistics.)

How to contribute in Wikipedia?
Contributing to wikipedia is quite an easy job, though the process of contributing as explained by Wikipedia is too cumbersome that may scare away the possible contributors.
First of all create a username in Wikipedia, its recommended (by me) because you can access your contribution list & watch list. Although you can contribute without getting signed up but you can't access your contribution list & you can't observe which of yours contribution are retained on the Wikipedia & which are removed.
There are many ways you can contribute to the Wikipedia, contributing the pictures are quite easy. You have to search in Google images for free images. (use advance preferences as shown in picture)

You can use your own photos taken by yourself (It will be better if you get it's copyright using some copyright providers like Creative Commons). Upload the picture to Wiki-media Commons i.e. the repository of all Wikipedia files.
Wikipedia hates illegal use of copyrighted content.
You can also add some useful articles in the Wikipedia if its not there. You can edit some content which you find appropriate to be appended or added. In editing a content or adding new article, the important issue is citation. You must refer to a reliable source of information that can be cross verified or your amendment will be rolled back by any higher authority. Mostly reliable source is another reliable site. You can't give reference of a forum or similar sites, since the information present there is questionable. For further information visit this link.

Contributing to Wikipedia is like a community service but in my opinion its far greater than community service because your fruits of contribution nurtures the whole world. So sign up to Wikipedia & start contributing.