I often find it helpful to spin up a new Pressflow instance for local development and testing, without any fancy APC or Varnish configuration, and without any source control. Here's a quick way to do that.
First, set up your MAMP so it it works with Virtual Hosts. This gives us the ability to run multiple webroots of Drupal on the same IP address (in this case, on your local machine.)
By default, most Drupal setups have an upload file size limit of 2 megabytes. That's enough for uploading most content like images and short Word documents and PDF files. But start uploading larger files like audio or video, and you'll quickly run into this frustrating upload limit. Some video files can be hundreds of megabytes! Here's how you can get around the limit.