updates to contribution guidelines

Author: saehejkang

CONTRIBUTING.md

@@ -2,6 +2,15 @@
 
 Contributions to Containerization are welcomed and encouraged.
 
+## Index
+
+- [How you can help](#how-you-can-help)
+- [New to apple/containerization?](#new-to-applecontainerization)
+- [Submitting issues and pull requests](#submitting-issues-and-pull-requests)
+- [New to open source?](#new-to-open-source)
+- [AI contribution guidelines](#ai-contribution-guidelines)
+- [Code of conduct](#code-of-conduct)
+
 ## How you can help
 
 We would love your contributions in the form of:
@@ -14,15 +23,19 @@ We would love your contributions in the form of:
 
 Anything else that could enhance the project!
 
-## Submitting Issues and Pull Requests
+## New to apple/containerization?
+
+To see the current list of maintainers, please refer to the  [MAINTAINERS.txt](MAINTAINERS.txt) file in the repository.
+
+## Submitting issues and pull requests
 
 ### Issues
 
 To file a bug or feature request, use [GitHub issues](https://github.com/apple/containerization/issues/new).
 
 🚧 For unexpected behavior or usability limitations, detailed instructions on how to reproduce the issue are appreciated. This will greatly help the priority setting and speed at which maintainers can get to your issue.
 
-### Pull Requests
+### Pull requests
 
 We require all commits be signed with any of GitHub's supported methods, such as GPG or SSH. Information on how to set this up can be found on [GitHub's docs](https://docs.github.com/en/authentication/managing-commit-signature-verification/about-commit-signature-verification#about-commit-signature-verification).
 
@@ -55,23 +68,56 @@ We do not currently accept contributions to add editor specific additions to the
 git config --global core.excludesfile ~/.gitignore
 ```
 
-#### Formatting Contributions
+#### Formatting contributions
 
 Make sure your contributions are consistent with the rest of the project's formatting. You can do this using our Makefile:
 
 ```bash
 make fmt
 ```
 
-#### Applying License Header to New Files
+#### Applying license header to new files
 
 If you submit a contribution that adds a new file, please add the license header. You can do this using our Makefile:
 
 ```bash
 make update-licenses
 ```
 
-### AI Contribution Guidelines
+## New to open source?
+
+### How do I pick something to work on?
+
+In case you don't have anything specific to work on, you could
+start off by picking a [good first issue](https://github.com/apple/containerization/contribute). Before you start
+working on an issue:
+* Check the comments, assignees, and any references to pull requests — make sure
+  nobody else is actively working on it, or awaiting help or review.
+
+* If someone is assigned to the issue or volunteered to work on it, and there
+  are no signs of progress or activity over at least the past month, don't
+  hesitate to check in with them — it might be that the person moved on.
+
+* Leave a comment that you have started working on it.
+
+### Getting help
+
+Once you start working on the issue, you will inevitably end up having a lot of questions. Don't be afraid to ask for help! The codebase is large and wrapping your head around it will take time. When asking for help, prefer giving as much information as possible, while highlighting the parts that you think are important. Refer to the [New to apple/containerization?](new-to-apple/containerization) section for the appropriate maintainers to ping.
+
+### I didn't get a response from someone. What should I do?
+
+It's possible that you ask someone a question in a issue/pull request and
+you don't get a response as quickly as you'd like. If you don't get a response
+within a week, it's okay to politely ping them using an `@` mention with a
+reminder. If you don't get a response for 2-3 weeks in a row, please ping
+someone else.
+
+### I can't finish the contribution I started. :frowning_face:
+
+Sometimes an issue ends up bigger, harder, or more time-consuming than expected — **and that’s completely fine.**
+Be sure to comment on the issue saying you’re stepping away, so that someone else is able to pick it up.
+
+## AI contribution guidelines
 
 We welcome thoughtful use of AI tools in your contributions to this repository. We ask that you adhere to these rules in order to preserve the project's integrity, clarity, and quality, and to respect maintainer bandwidth:
 
@@ -81,6 +127,6 @@ We welcome thoughtful use of AI tools in your contributions to this repository.
 
 AI tools should be used to **enhance, not replace** the human elements that make OSS special: learning, collaboration, and community growth.
 
-## Code of Conduct
+## Code of conduct
 
 To clarify of what is expected of our contributors and community members, the Containerization team has adopted the code of conduct defined by the Contributor Covenant. This document is used across many open source communities and articulates our values well. For more detail, please read the [Code of Conduct](https://github.com/apple/.github/blob/main/CODE_OF_CONDUCT.md "Code of Conduct").