diff --git a/REVIEWING.rst b/REVIEWING.rst
index 9b272bb..9ad9ea0 100644
--- a/REVIEWING.rst
+++ b/REVIEWING.rst
@@ -21,6 +21,15 @@
 to a Gerrit review.
 
 
+Execution time
+--------------
+While checking in the job logs that a new test is actually executed, also
+pay attention to the execution time of that test. Keep in mind that each test
+is going to be executed hundreds of time each day, because Tempest tests
+run in many OpenStack projects. It's worth considering how important/critical
+the feature under test is with how costly the new test is.
+
+
 Unit Tests
 ----------
 
@@ -48,6 +57,17 @@
 abstract the duplicated code into a function or method.
 
 
+Tests overlap
+-------------
+When a new test is being proposed, question whether this feature is not already
+tested with Tempest. Tempest has more than 1200 tests, spread amongst many
+directories, so it's easy to introduce test duplication. For example, testing
+volume attachment to a server could be a compute test or a volume test, depending
+on how you see it. So one must look carefully in the entire code base for possible
+overlap. As a rule of thumb, the older a feature is, the more likely it's
+already tested.
+
+
 Being explicit
 --------------
 When tests are being added that depend on a configurable feature or extension,
@@ -60,8 +80,8 @@
 
 Configuration Options
 ---------------------
-With the introduction of the tempest external test plugin interface we needed
-to provide a stable contract for tempest's configuration options. This means
+With the introduction of the Tempest external test plugin interface we needed
+to provide a stable contract for Tempest's configuration options. This means
 we can no longer simply remove a configuration option when it's no longer used.
 Patches proposed that remove options without a deprecation cycle should not
 be approved. Similarly when changing default values with configuration we need