All crypto is just as strong as your password.
There are different philosophies… but one everyone is sure about:
The longer, the better. https://xkcd.com/936
Do not use the same password everywhere!
Have at least different security-levels in passwords, e.g. a basic one for strange webservices you dont trust at all, some more, and at the end the strongest one in different combinations for you most important things!)
Do not use any words from a dictionary!
Add some special characters!
A good thing is to mix up languages and letters in one sentence.
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Make it long
Make it practical
Don't make it personal
Keep it secret
Make it unique
Keep it fresh