The plant profiles section starts with my pictures. I hike all over the Bay Area and Northern California. Along the trail, I select plants to photograph for identification. I often try to guess. I may think I know a plant, and I'm looking for confirmation. Sometimes, like the Calochortus albus - White Globe Lily, I have absolutely no idea. When I get home, I crop the photos so that the most pertinent parts are clear.
I seriously love this site. I recommend it over every other plant ID app that I've ever seen. It is not only great at IDs but there's a fantasttic community to back it up. If you're not already a member, join (it's free). I upload all the pictures I take of a single specimen (and I alwas take more than one), and see what it suggests.
I get into the nitty gritty with my books and websites. On the web, I always look at other observations of the species on iNaturalist, Wikipedia, and if available, eflora and Calflora. These are the links I always add to the Plant Profile page. If I'm confident, I tag my iNaturalist observation with an ID and wait for the community to confirm.
In the process, I always deepen my knowledge - not just about the specific plant in question, but also about the traits, the botanical vocabulary, other species that look alike, or that are closely related. At the end, I try to distill the important bits, and that's what ends up on the Plant Profiles page.
phylum: Tracheophyta
class: Magnoliopsida
order: Asterales
family: Asteraceae
subfamily: Carduoideae
tribe: Cardueae (Cynareae)
sub-tribe: Carduinae
genera: Carduus, Cirsium, Cynara, Silybum (Purple Spiny Thistles) {partial} {coming soon}
order: Caryophyllales
family: Polygonaceae
subfamily: Polygonoideae
genus: Rumex (Dock and Sorrel)
order: Malvales
family: Malvaceae
subfamily: Malvoideae
genus: Malva (Mallow)