If you're wanting to join one of the knowledge only groups, you'll need to post proof of your knowledge. Generally this just involves posting projects you are proud of. Or telling us about projects you have worked on, and how you applied your specific knowledge.
Knowledge Groups:
There is also the 'Respected Group', however this is non-apply able. The only way to obtain this rank is to become a community asset (Someone the community relies upon).
After you've created your thread, the community will give you feedback. The bar is low so you're likely to get accepted.
Knowledge Groups:
- Reverse Engineer
- Java Expert
- Dot Net Expert
- Native Expert
- Android Expert
- iOS Expert
- Frontend Expert
- Windows Expert
- Linux Expert
- Database Expert
There is also the 'Respected Group', however this is non-apply able. The only way to obtain this rank is to become a community asset (Someone the community relies upon).
After you've created your thread, the community will give you feedback. The bar is low so you're likely to get accepted.