1: Find out your competitors backlinks through your favorite website/tool. 2: Open the website and look for a contact form or an e-mail address. If there's none available, look up their whois. 3: Find out the name of your competitor, again, through whois. If you can't find it, make up a name. Register an e-mailaddress with this name. 4: Contact the websites that have backlinks, saying something like: 'Thanks for linking to my website, domain.com (competitors domain). Tell him you don't have acces to said domain anymore, so you made a new website, domain.com (Your own domain). Tell the person the other website will go offline soon. 5: Hope for the best. This might be a little bit unethical, but it is extra efficient, cause not only do you gain backlinks, your competitor loses them.