Sometimes we find it too hard and unable to understand the facts behind drop in the rankings and traffic. One of the best places as a webmaster/website owner is to visit the Links to Your Site section in the Google webmaster tools. Review all the three sections "Who links the most", "Your most linked content" and "How your data is linked" and record all changes to compare with your previous data to observe and understand the changes. I recommend, all the webmasters should maintain a back-up of these metrics periodically and If you don't have the past data please start taking backup's from now onwards. In either case, follow the below steps:
1) Identify the links which are relevant and try to analyse the strength of the links.
2) Identify the links which are not relevant.
3) Try to find out the links with repetitive/irrelevant anchor text from both sets you identified in step 1 and 2.
4) Based on the Strength and Anchor Text of the links and other priorities (if any) separate the links identified in step 1 which you want to discontinue.
5) Club the links from step 2 and 4 and prepare your disavow file.
6) Click this link https://www.google.com/webmasters/tools/disavow-links-main
7) Select the portal to which you want to upload the disavow links.
8) Click "Disavow Links" Button.
9) Choose the file from your local Computer.
What happens once you submit the file?
Once it has been updated you will receive a message with subject line http://www.example.com/: Disavowed links updated and it may take while to get the changes effected.
Note: It is always recommended to contact the relevant webmaster to either tweak the anchor text if you believe the link good enough to continue or to remove the link before submitting it into the disavow file.
The other site owners may seek money to remove the links from their website. I recommend not to encourage such things and carry on including those links into disavow file. Do the same with non-response scenarios.