As I understood, i can trust only that sites that have wikipedia pages. Like there can be the company history. Also, it means that some guys already checked them, including teachers. they should've been judged plenty of times!
If you're looking for companies, I'd agree that you should be wary of any recommendations you get here. I'd start by browsing through company sites. See if the content appears to have been written by a native English speaker--it's surprising how often it doesn't, and if they're not going to catch grammatical errors on their website, it's hard to imagine that they'll reliably do so with your paper. If you're not a native English speaker, have a friend scan through for you. Usage errors like that are usually fairly easy to spot.
There are a few other indicators of reputability that you can research as well. It's easier for offshore companies to register in some states than others, for instance. BBB registration can also be a clue.
Trying your luck with a freelance writer is an option as well. If you know anyone who's ordered essays before, ask them for a referral. If that's not an option, a lot of the folks on this site are engaged in the business in some capacity or another. Some accounts are legit; others are scam accounts used primarily to promote one's own company or defame the competition.
There are other threads that deal with how to go about sorting the good for the bad, although there aren't any foolproof methods. The simplest way is just to read through the forums and see who seems to be participating in a fair and straightforward way; make sure to take advantage of the search function to check out posting history (you may have to fiddle with the settings so you can search entire posts rather than just thread titles). Same rule applies as for evaluating company websites: keep your eyes peeled for for shoddy English.
Anyway, you have my sympathy; I know can be a confusing and nerve-wracking world to engage with at first. Just remember that you only have to find one honest, reliable source--whether a freelancer or a company--and you're set; you won't have to go through this process again. There are plenty of those professionals out there (and some here on these forums as well). This business couldn't function otherwise.
At the end of the day, scams and scammers need something legitimate to feed off, and that legitimate thing is a fair-and-square, fee-for-service exchange between educated professionals who are in the business because it's engaging and surprisingly fun (at least for the nerdier among us), and students who need a hand in an increasingly competitive and financially-risky academic environment.
Good luck!
