Our group is using CiviCRM to house membership data for a small food cooperative. We've lost our web developer and we're trying to get all of our data out of CiviCRM with only the user interface tools. I've tried the various search tools, but the results are perplexing. When I go to Search >> Find Activities and search without any filtering, I get 124 activities. When I do Custom Searches >> Activity Search without any filtering, I get 898 activities. The discrepancy between the two is confusing, but if I assume the custom searches gives me the complete list, then my problem is that custom search doesn't allow me to specify which fields to download. The regular activity search provides over 80 data points whereas custom search only gives 13 data points. Feel free to point me to documentation if it's covered out there. Thank you.
The difference in counts might be explained by the fact that at one time Find Activities only returned results where the With Contact field wasn't empty, and a quick check on the public demo suggests that's still true.
That also seems true for Advanced Search.
You can also try Search Builder, but the list of fields is minimal.
If you're using Drupal, you could try creating a View on the Drupal side that lists the activities.
Custom searches often have built-in filters that may not be very obvious, where as built-in searches allow you to query data with limited restriction. My suggestion to you would be to create a smart group of "All Contacts" (if you don't already have one), then use Search > Advanced Search and change the Display Results As filter as needed - e.g. start with Display Results As = Activities, then work through the list of entities as desired:
Hope this helps!