How to proceed when a bug in open source libraries is suspected?

Question

We are using some open source libraries in our projects. Sometimes there are some issues found in some of them (most likely library bugs, but it may also be a wrong usage from our side, especially when sometimes documentation is not exactly 100 % complete). As the libraries are often quite complex, debugging them to pinpoint the source of the problem is sometimes quite hard. Can you help me to summarize what other options are there and how to exactly proceed with them?

I have just recently hit some strange problems when using TCMalloc (Google scalable memory allocator) on Windows, so I would most welcome answers which would apply to this particular library, but more general answers are good as well.

1) Ask the maintainer/owner of the project for assistance. How can this be done?

2) Hire someone to identify and fix the issue. How to do this? How can I find someone with enough expertise in some particular library?

... any other options?