A very good place to start these days is at https://discourse.wicg.io/. That’s the Web discussion forum for the Web Platform Incubator Community Group (WICG), a W3C Community Group (CG).
The WICG is open to participation from absolutely anyone, and was created through collaboration with all major browser-engine projects (Webkit/Safari, Gecko/Firefox, Edge/MSIE, Blink/Chrome) expressly for the purpose of providing everybody with “a lightweight venue for proposing and discussing new Web-platform features”.
The WICG just started recently but has already published Contributing New Proposals guidelines.
Here from those guidelines are the key steps it outlines for the development of a new feature:
- State the problem
- Join the group
- Evaluation
- Use cases
- Advocate
- Specify it
- (Bonus points) Implementation
That outline’s based on looking at previous successes in getting new features into the platform (e.g., the responsive-images <picture>
element and srcset
attribute) and sort of reverse-engineering the steps that led to those successes, documenting them, and optimizing for them.
As somebody who’s been closely involved in work on the platform for a lot of years now, I cannot overstate the importance of step #1 from that outline, State the problem.
The most progress gets made with the least amount of acrimony when people show up with very clear problem descriptions first, and ask others for ideas about how to solve the problem—as opposed to, say, showing up with a solution already in hand themselves, and being already over-invested in their own idea of what the right solution is.
There’s lots of positive energy behind the WICG and it’d be great to get more people involved in it.