But Craig's question was just, "what resolution setting should I use on my phone camera?"
So, back to that question, I'll add to what I said in Post#2:
Why not go ahead and keep the phone camera set at maximum resolution? After all, most phones have lots-o-memory these days and probably a memory card as well, so there's plenty of room and maximum resolution will give you more options.
The main reason "why not" is because before you share the photo you'll have to -- or at least you really should -- smallify the image (reduce the resolution) since whomever you're sharing it with doesn't need/want an image that's 3500 pixels wide. If you're emailing it then it's a huge attachment and if you're uploading it it's a slow upload.
What do I do? I shoot at full resolution (to give me more options) but I have software that can batch-wise reduce a bunch of photos all-at-once to a civilized resolution suitable for Internet sharing. I recommend
Irfanview -- maybe the most popular free image editing software -- for this simple task (and many others).
Send me a PM, Craig, if you have any questions about using Irfanview. I have Lightroom and Photoshop but I still use Irfanview for simple cropping/resizing for non-critical Internet-sharing purposes.
IMHO.
By the way: If the phone camera has a "quality" setting, aka, jpeg compression setting (I don't know if it does, my stock phone-camera app doesn't) you should set it for maximum quality -- the least amount of jpeg compression. This really does matter at any resolution you choose. This gives you the option of manipulating a high-quality image (if you so choose) rather than starting with one at compromised quality that only gets worse if/when you re-save it.