Magento Caching

I am an experienced programmer and developer, but new to Magento. I’m working through things, and getting more comfortable every day. Something that has been frustrating is the various caching mechanisms in play, and their impact on changes to various design files and configuration. It’s had me spinning my wheels a few times, seemingly nothing would work – me thinking I had no idea what was going on – and a server reboot seemed to magically put everything in place. Currently, I’m updating some content blocks, and for the life of me I cannot see the changes I am making. Similarly, I’ve made edits to pages that seemed to preserve and hang onto their old content. I’ve created xml configuration-based files that have done nothing (except apparently on server reboot).

What am I missing here? Note that I understand the concept of the Magento system caches – but obviously not everything. I have configured and am using Varnish if that makes a difference. Magento developers here: When you make changes to configuration and/or theme related files, how do you test and/or view the changes immediately?