[lervag]

I use two things:

* A password manager (PasswordStore [0]), in which I may make entries without passwords but where I indicate my ID on a given account.

* A personal wiki in which I may indicate for something that I have an account connected to e.g. Google or whatever.

When I come to some service that I vaguely remember having used before, I will find the necessary info either in my personal notes or in my password manager.

[0]: www.passwordstore.org