Writing this down since it may be useful for other beginners:
My biggest confusion at first was that my edits didn’t show up right away, and the interface provided no hint about why that was happening (so I wondered if I was doing something wrong). I googled it and found out that delays are normal, but the estimate in the FAQ said “a few minutes”, which hasn’t seemed accurate for me - my edits often seem to take hours to show up. So I just have to do my edits and then check back on them later; as a newbie, it’s important to me to verify my edits to make sure I did them correctly. Eventually I read the extended technical explanation for delays on the Q&A site, and it helped me be patient with the process; I’m not a programmer, but I work with software, and I can appreciate descriptions of complicated caching systems. :)
My next stumble was when I found editing a set of park boundaries difficult to do properly (since attempting to fix the boundaries seemed to delete the adjoining streets). I asked the OSM IRC channel for help (which I found by googling “OSM IRC”, since I’m familiar with IRC and like using it), and their comments suggested trying a different editor - which worked! Fixing the boundaries was much easier in iD than in Potlatch (which I’d been using since it’s the default editor), even though I’ve stuck with Potlatch for most edits since it provides lots of point-and-click options for adding and annotating points of interest and other details. I learned that if something is hard/tricky, I should try a different editor.
I only ran into the Good practice wiki page and Bing wiki page by accident (when trying to help an even-newer person on IRC), but they’re very helpful. On the “good practice” page, “One feature, one OSM element” confirmed for me a best practice I’d guessed about, and I appreciated learning why it was OK to trace from Bing (I’d been wondering about that).
I’d heard about the Humanitarian OpenStreetMap Team a while back via people I follow on Twitter and via a presentation at OSCON about HFLOSS, and checking out the HOT OSM site turned out to be a good candidate for solving my current stumbling block of “what should I try next after fixing the obvious problems in my neighborhood?”: the Tasking Manager - nice!
Postscript: I just noticed another issue - I’d had this New Diary Entry page open for several days while writing down notes, and finally I clicked “Preview” and confirmed that it looked good enough to post, but when I clicked “Save” I got an error message - I was no longer logged into OpenStreetMap! I would have lost my post text if I hadn’t had a copy of it in a text editor. It would be nice for “Preview” to somehow check that the person is still logged in, to avoid losing posts.