Update PR template with more explicit instructions (#496)

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,12 +2,21 @@
 
 - ...
 
-## PR checklist for schema changes
+## Checklist
 
-<!-- If the current schema version already ends in "-alpha", then delete the first two items: -->
-- [ ] Update the version string in `docs/format/source/conf.py`, `core/nwb.namespace.yaml`, and `/core/nwb.file.yaml`
-  to the next version with the suffix "-alpha"
-- [ ] Add a new section in the release notes for the new version with the date "Upcoming"
-- [ ] Add release notes for the PR to `docs/format/source/format_release_notes.rst`
+For all schema changes:
+- [ ] Add release notes for the PR to `docs/format/source/format_release_notes.rst`.
+
+If this is the first schema change after a schema release (i.e., the version string in `core/nwb.namespace.yaml` does not
+end in "-alpha"), then:
+- [ ] Update the version string in `core/nwb.namespace.yaml` and `core/nwb.file.yaml` to the next major/minor/patch
+  version with the suffix "-alpha". For example, if the current version is 2.4.0 and this is a minor change, then the
+  new version string should be "2.5.0-alpha".
+- [ ] Update the value of the `version` variable in `docs/format/source/conf.py` to the next version **without** the
+  suffix "-alpha", e.g., "2.5.0".
+- [ ] Update the value of the `release` variable in `docs/format/source/conf.py` to the next version **with** the suffix
+  "-alpha", e.g., "2.5.0-alpha".
+- [ ] Add a new section in the release notes `docs/format/source/format_release_notes.rst` for the new version
+  with the date "Upcoming" in parentheses.
 
 <!-- See https://nwb-schema.readthedocs.io/en/latest/software_process.html for more details. -->