Reporting bugs is already a good way to help if you do it well. (I mean with enough details so it doesn’t end like a waste of time.)
If you speak several languages, you can participate in localization efforts on Pootle but also on Polyglot.
You can hunt for typos everywhere, apps, docs, web site, package recipes.
I think that there a need for some visual things, like hvif icons for some apps.
You may have noticed there is almost no changelog in HaikuDepot. Maybe some help is needed with that.
Speaking as a non developer myself also, maybe you can check out our great haikuporter tool and check haikuports if there is an interest for you.
Or you can write tutorials, help by translating tutorials or check translattions of our tutorials for our haiku knowledge base http://www.besly.de