How do you handle updating project dependencies?

Most projects use third-party packages as dependency, no matter what languages you use.

How often do you update your dependencies? Do you automate it, and if yes what tool do you use? Do you use single commit for updating each dep or use one commit for all the deps? Some libs don't provide changelogs that makes it hard to know the changes between versions, what are your thoughts on them (are you using them anyway)? Any other thing that you consider when updating deps?

Suggestions, anecdotes, any kind of experiences welcome!