Hi Igor!
While there are many different attributes that can make a link valuable to your specific site, a very over-arching method for checking link quality would be to sort by Domain Authority. This will give you the most authoritative sites that link to your competitors. Please keep in mind that it does take some investigation to sort through this list to find high quality opportunities.
For example, a competitor may have a link from a Wordpress blog that shows a 100 for the Domain Authority number. In reality, that blog may have very low Page Authority, may actually have low authority and low readership.
I'm a fan of Eric Ward's golden rule. Review link opportunities and if they provide your site with an opportunity to earn some quality referral traffic as a result, then they are likely "good" links to pursue. If not, it may be better to pass.
Diversifying your traffic sources through quality links is much more valuable long-term than simply pursuing links to obtain better search rankings.
Let me know if that makes sense and I'll do my best to help and/or elaborate!
-Ricky