diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 981bdbb81..af0bbde57 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -54,7 +54,12 @@ Modules that are only available for Python 2 are not listed in `VERSIONS`.
 
 ### Third-party library stubs
 
-Modules that are not shipped with Python but have a type description in Python
+We accept stubs for third-party packages into typeshed as long as:
+* the package is publicly available on the [Python Package Index](https://pypi.org/);
+* the package supports any Python version supported by typeshed; and
+* the package does not ship with its own stubs or type annotations.
+
+Stubs for third-party packages
 go into `stubs`. Each subdirectory there represents a PyPI distribution, and
 contains the following:
 * `METADATA.toml`, describing the package. See below for details.
@@ -66,7 +71,12 @@ contains the following:
   and also with Python 2 if `python2 = true` is set in `METADATA.toml` (see below).
 * (Rarely) some docs specific to a given type stub package in `README` file.
 
-When a third party stub is
+The fastest way to generate new stubs is to use [stubgen](https://mypy.readthedocs.io/en/stable/stubgen.html),
+a tool shipped with mypy. Please make sure to use the latest version.
+The generated stubs usually need some trimming of imports. You also need
+to run `black` and `isort` manually on the generated stubs (see below).
+
+When a third party stub is added or
 modified, an updated version of the corresponding distribution will be
 automatically uploaded to PyPI within a few hours.
 Each time this happens the least significant