diff --git a/resources/ssl/README b/resources/ssl/README
--- a/resources/ssl/README
+++ b/resources/ssl/README
@@ -10,3 +10,16 @@
 or create a file (or symlink) in this directory named "custom.pem".
 
 If "custom.pem" is present, that file will be used instead of "default.pem".
+
+If you receive errors using your "custom.pem" file, you can test it directly
+with `curl` by running a command like this:
+
+  curl -v --cacert path/to/your/custom.pem https://phabricator.example.com/
+
+Replace "path/to/your/custom.pem" with the path to your "custom.pem" file,
+and replace "https://phabricator.example.com" with the real URL of your
+Phabricator install.
+
+The initial lines of output from `curl` should give you information about the
+SSL handshake and certificate verification, which may be helpful in resolving
+the issue.