Update readme

README.md

@@ -45,3 +45,8 @@ GitLab LFS client install and usage:
 Gitlab Kanban
 - http://kanban.leanlabs.io
 - https://gitlab.com/leanlabsio/kanban
+
+Tips & Tricks
+
+- Database Console: `sudo -u gitlab-psql /opt/gitlab/embedded/bin/psql -h /var/opt/gitlab/postgresql/ gitlabhq_production`
+- Mattermost CLI: `/opt/gitlab/embedded/service/mattermost/i18n` and then `sudo -u mattermost /opt/gitlab/embedded/bin/mattermost -config=/var/opt/gitlab/mattermost/config.json -help`