Improve Contributing Guidelines

CONTRIBUTING.md

@@ -82,7 +82,7 @@ Detailed explanation:
    git checkout -b <topic-branch-name>
    ```
 
-5. Run `make lint` to check that your page(s) are correct.
+5. Run `make lint` to check that your page(s) are correct. Try to run the commands you are describing to ensure the syntax is correct.
 
 6. Please use the following commit message format: 
    `<command>: type of change`.
@@ -103,14 +103,30 @@ Detailed explanation:
 8. [Open a Pull Request](https://help.github.com/articles/using-pull-requests/)
     with a clear title and description.
     
+    If page is not about a standard Unix/Linux tool, please include a link to the tool home page.
+    
+    If you are changing something non-trivial, not just adding a page for a new tool, please describe why you are doing this.
+
 9. Use Git's
    [interactive rebase](https://help.github.com/articles/interactive-rebase)
    feature to tidy up your commits before making them public.
+   
+   If you are not familiar with `git rebase`, it might be helpful to check out these video tutorials:
+   - [Git Rebase: squash last commits](https://www.youtube.com/watch?v=qh9KtjfjzCU)
+   - [Learning Git Tutorial: Interactive Rebasing](https://www.youtube.com/watch?v=NW46XmvJh5Q)
+   
    In most cases it is better to squash commits before submitting a pull request.
 
-10. If you are asked to amend your changes before they can be merged in, please
+10. If you do not want to do a rebasing, you can overwrite your last commit in pull request, while you have only a single commit. You can achieve this with `git commit --amend` command.
-   use `git commit --amend` and force push to your remote feature branch.
+
-   You may also be asked to squash commits.
+   ```bash
+   # When you are on topic branch of your pull request
+   # Fix your files
+   
+   git add .              # Register edited files
+   git commit --amend     # Do amended commit
+   git push --force       # Overwrite your branch
+   ```
 
 
 ## Licensing