How to choose a VPN: what to check before installing
Start with an uncomfortable question
What problem are you trying to solve? The answer completely changes what you should look for.
Encrypting your connection on public networks, stopping your carrier from logging the domains you visit, and reaching services restricted on a particular network are three different goals. No VPN is equally good at all three.
If your answer is "I want to be anonymous", no VPN will do. That is the most useful conclusion in this article.
The five criteria that matter
1. What it logs, in detail. Look for concrete retention periods and concrete data types. An unqualified "zero logs" is a marketing line: any service with a website has access logs on that website.
2. How it is funded. If it is free and the site does not explain this, stop there.
3. Where it is incorporated. That determines which laws apply and to whom it answers. If it is stated nowhere, that is a signal.
4. Which permissions the app requests. A VPN needs VPN permission and little else. If it asks for contacts, precise location or file access, ask yourself what for.
5. What it promises. The more absolute the language, the more scepticism it deserves. "Total anonymity", "undetectable", "complete protection" are warning signs, not quality marks.
What you can verify yourself
Read the privacy policy, dull as it is. If it is generic enough to fit a shoe shop, somebody copied it.
Look the company up in a company register. If it claims to be incorporated somewhere, that should be checkable.
Check the permissions on the store listing before installing.
Check that their links work. A privacy policy that errors out is a sign of neglect.
On "best VPN" lists
A good share of those lists are affiliate content: whoever publishes them earns a commission per subscription. That does not automatically invalidate them, but it explains why the ranking changes so much between sites.
Use them to discover options, not to decide. The decision should come from the five criteria above, checked by you on each provider's own site.