Finishes contributing guide

CONTRIBUTING.md

@@ -9,7 +9,7 @@ GitLab can be found in [Boas práticas do uso do Git e GitLab no LEG][]
 
 ## Workflow
 
-In `legTools` we use the Gitflow workflow, which can be viewed in this
+In `legTools` we use the Gitflow workflow, which can be viewed in these
 two links: [A successful Git branching model][], and
 [Atlassian tutorial][].
 
@@ -31,15 +31,35 @@ branch to make sure that what you are trying to do is not already being
 done. Then create a new branch, based on the `devel` branch, and make
 changes in this branch. When you are ready to submit your changes,
 please open a Merge Request (MR), and explain in details your
-implementation, and how this could be beneficil to the project.
+implementation, and how this could be beneficial to the project.
 
 Also, if you're not sure about how to do something, but have an idea for
 the project, feel free to open an issue and explain what you want from
 there.
 
+## General rules for commits
+
+Commits are a very important part of git. The four most important rules
+to follow are:
+
+1. **Commit often**
+2. **Don't commit half-done work**
+3. **Test before you commit**
+4. **Write good commit messages**
+
+For more detailed explanation and specific guidelines, see
+[Criando commits][] in [Boas práticas do uso do Git e GitLab no LEG][],
+and [Version Control Best Practices][].
+
+****
+
+Fell free to contact us (via email or an issue) if you have any doubts
+about contributing.
 
 <!-- links -->
 
 [A successful Git branching model]: http://nvie.com/posts/a-successful-git-branching-model/
 [Atlassian tutorial]: https://www.atlassian.com/git/tutorials/comparing-workflows/feature-branch-workflow
 [Boas práticas do uso do Git e GitLab no LEG]: http://git.leg.ufpr.br/leg/gitlab-rautu/blob/master/CONTRIBUTING.md
+[Version Control Best Practices]: http://www.git-tower.com/learn/git/ebook/command-line/appendix/best-practices
+[Criando commits]: http://git.leg.ufpr.br/leg/gitlab-rautu/blob/master/CONTRIBUTING.md#criando-commits