Probably the same way you get your information. Reading and learning.
You can’t trust VPN providers claiming they don’t keep logs. It’s been shown time and time again that they are not truthful. What you have to look for is independent audits or research. There are some good comparison charts, but don’t get them from the big sites like Forbes etc. Most of them are sponsored articles paid by the VPN providers. Instead look for Google sheets etc.
For example, a popular VPN provider is PIA. Before they were acquired by former malware distributor Kape they were ok. Now I wouldn’t trust them more than a free VPN provider.
As a guideline you also shouldn’t use a VPN provider located in a country part of the Five Eyes intelligence sharing agreement. So don’t use a VPN provider based in the US, UK, Australia, New Zealand and Canada.
There’s so much to VPN services and what to look for to list and I’m not going to debate who’s the best. I’m just trying to provide some useful information. People can do what they want.
To make it easier for someone, I’ll mention one of the safest VPN providers I would trust. Admin can remove it if it’s seen as marketing. It’s Swedish based Mullvad. But they are not cheap.
Anyway, there’s a lot more to online privacy. DNA leaks, browser type etc.