If you're eager to get your first OpenLayers map on a page, dive into the quick start.
For a more in-depth overview of OpenLayers core concepts, check out the tutorials.
Make sure to also check out the OpenLayers workshop.
We have put together a document that lists Frequently Asked Questions (FAQ) and our answers. Common problems that may arise when using OpenLayers are explained there, and chances are you'll find an appropriate solution in this document.
If you cannot find an answer in the documentation or the FAQ, you can search Stack Overflow. If you cannot find an answer there, ask a new question there, using the tag 'openlayers'.