The short answer: Go for EVERYTHING you see. Even the smallest, least conspicuous plant growing in a crack of the pavement is important for the survival of another lifeform and worth recording. And, take pictures of details, stems, leaves, from various angles, and make sure you include a view of the environment where you saw it. Speaking of plants, don’t confine yourself to nice shots of flowers. Please also record what the plant looks like as it dies, dries up, because some other user may find that useful, because the iNat algorithm has to learn too.
The long version: I started getting serious about learning about the plants growing in my yard when I needed to fence out those that could be lethal to plant-eaters (I don’t mean cats and dogs nibbling on the odd leaf, I mean animals that actually live off plants) and realized my knowledge was entirely theoretical – while I knew the NAMES of the plants that could be dangerous, I had NO IDEA of how to recognize them, especially when they were not flowering, which is when you really need to recognize them either to uproot them or fence them out. Books and internet sites are helpful to a point, because most often you only get to see close-ups of flowers. What about when these plants are still small? Or dry? What do their seeds look like?
Phone apps were a bit more useful, but there were issues of reliability. At first I tried out PlantNet, which has some virtues, yet didn’t convince me when I tested it with plants that I knew well. PlantNet is fine for folks who want to know what that lovely plant on that lady’s balcony is called. One app that was more reliable in my experience was Flora Incognita, which seems a bit more knowledgeable about central European plants than PlantNet, and was good with grasses. Ultimately I ended up with iNat because there were actual people checking, one could ask a question and get an answer! :-) It was more like being out there with someone else who was more knowledgeable than me and whom I could learn from.
Yet even on iNat there are plenty of sightings of flowering plants, often without even a view of the stem or the leaves. Lowly, common, uninteresting plants? Much rarer than the rarer plants that people tend to photograph when they stumble over them while out up in the mountains.
Some of the plants growing in my yard that I knew to be pretty common had no observations in my area. It wasn’t the plant that was rare, what was rare was people considering them important enough to be photographed.
That is huge failure, if you ask me. Because if we seriously wish to conserve biodiversity, we need to know what plants depend on what insects and viceversa. A lowly curly dock (Rumex crispus) is considered ugly and useless according to some (check a thread title in this forum). From the point of view of several species of butterflies and moths, however, that plant is VITAL.
What’s the point of being able to recognize exotic stuff growing in pots on someone’s deck but not knowing about ‘useless’ plants like these:
https://www.inaturalist.org/observations/112079735
https://www.inaturalist.org/observations/115474259
Why complain about the loss of insects and the disappearance of butterflies and then kill every ‘weed’ that dares assert its right to life?
As for uninteresting, common plants, and what they look like over time, here is an example:
https://www.inaturalist.org/observations?taxon_id=56138&user_id=olrett
The first time I saw this plant, I had no idea what it was. There were no flowers yet, and I couldn’t identify it. That’s why I am now making a point of recording them in various stages, to make life easier for those like me who come across it for the first time.
Learning about plants led to learning about insects and spiders and worms and all the other lifeforms making soil alive. I try to always add notes of what plant that particular insect is feeding on. During winter, when I am less out, I can go over the observations and integrate them.
Lately I find myself fascinated with behaviour. My latest observation is that dragonflies can be fooled by plastic surfaces and that lack of rain is a problem:
https://www.inaturalist.org/observations/125227154
https://www.inaturalist.org/observations/125833417