This depends on your use-case scenario but mostly you should look for a Proxy which does not get detected on various websites and if you use your Proxy for social media or an important purpose than your Proxy should be an Elite Proxy and should come with rotation option.
Well, seeing as i dont need anything special, i go by price. But even then its not that simple.
When i needed proxies at first, i checked marketplace for shared proxies and chose the cheapest ones. I asked for test proxies.
Then i saw who replied, how quickly they replied, and how they replied. I also tested the proxies.
I picked one provider. But i didnt know certain things. So i didnt know that i would have inconveniences with IP Authentication. And i couldnt change the IP im authenticated with. Id have to contact the guy every time. But even if i can change it myself, i cant know when my router will fart and my IP will change.
So now i went hunting again, looking for cheapest shared proxies with user-pass authentication. And of course, decent speed. Oh, and unlimited bandwidth.
So i found one. I started using it. But one day the guy says im using too much bandwidth. Im like what? You offer unlimited. He says yeah, but server overload youre using too much bandwidth bla bla yada yada.
So i go hunting again, double checking with providers all my concerns.
In the end, i found someone who really gave me all i wanted, and for a great price too. Also a great guy, who i could contact on skype if i had any issues. I rarely had issues, but the few times i did, he always replied, and always handled it. Fantastic.
So ive been using his proxies for about 1-2 years now. I always pay for 3 months. Often i pay again for another 3 months before my first 3 months expire. I ask him to pay, he sends me an invoice, and i pay. Its also a good deal that he accepts paypal, because it gives me the opportunity to empty out some money from a paypal account, to keep my paypal balance low.
And thats that
Oh, and never buy a large or long-term package from the get go. Because you need to test the proxies first, to see if uptime is as promised, to see if speeds are as promised, to see if unlimited bandwidth is for real. And you cant know these things after a few days of testing. Take at least a month to test, and go hard.
I select according by price. Always select private proxies and do not purchase the cheapest ones. I do not check proxies by blacklists, only by their performance with my tasks, after that I can decide should I purchase more from this provider or not
First of all - from price range that I can allow for the task, then test goes
-Features. Like how often can I cahnge the IP, whats the delay, is there a link to do this, connection protocols, can I set custom log/pass, ect
After this - final value for each provider that based on price and perfomance.