If you are going to start a website a blog or website in wordpress must install these plugins .

1-Akismet This plugin comes inbuilt in wordpress. This plugin removes and secure your wordpress sites from spams comments.

2- BackUpWordPress This plugin will help to take backup of SQL database of wordpress site.

3- Google XML Sitemaps This plugin generates XML sitemap of your website that contain each and every link in your site. This sitemap format is supported by every search engines. This is used to notify search engines about the links of your website

4- Google Analytic for WordPress This plugin will help you to get visitor stats of your website. You can add tracking of Google analytic through this plugin .You can see each and every visits , clicks on your website through this plugin

5-W3 Total Cache /W3 Super cache This plugin is the most downloadable and usable plugin in WordPress. This the the most fastest WordPress optimization plugin available free.

6-Contact Form 7 This plugin is used to make and manage various contact forms or feedback forms. With the help of this plugin, we can make different forms and can also customize them according to the needs .

7- All in One SEO Pack.-> This plugin is used to set titles, descriptions, keywords for different posts and pages.
This plugin is also used for Google Webmaster verification for different search engines like google ,bing, yahoo etc.. It is compatible with every WordPress versions