Lost my rankings, what to do?

[siva s]

This is usually a big drop in rankings, that happens over-night. If you notice that your site drops more than 10-20 positions on a multitude of keywords, this could indicate a penalty. A big difference between algorithmic and manual penalties is that the first ones are automatic and are usually released with various Google Updates, while the second ones are manually applied by a Google employee. Given the fact that Google made a habit out of making updates without clearly stating it, you should constantly monitor for ranking changes.

[AlyLauren]

Check your backlinks if they still perfectly work, update your old content and see if your website is still attractive enough or not.

[jackfernandos]

Rebuild quality back links with unique content and old spamy backlinks try to remove or edit. also you can add spamy backlinks in google webmaster's disavow tool.

[mukeshkr]

Now Recently Google updates comes for Mobile Web Pages if your web page is compatible with Mobile as well as PC Laptop then you will get better ranking author wise you lost some ranking.

If your website is not responsive then please make it responsive for mobile too.

[marka3441]

Concentrate more on OFF page SEO to bring it back, use these techniques:
Blogging
image sharing
video sharing
social bookmarking
business directory
business listing
Blog commenting

[marvinsam]

Some basic strategy to rank again
1 Do on page and off page
2 Social Book marking
3 Image backlinks
4 PPT submission
5 Forum posting