the first one is familiar to me, but i cant place it. is it a shrub? tree? maybe?
and totally it is tricky knowing how to even start when you dont what a plant is. i put in various keyword searches , but many times cannot find the name of a plant that way. though sometimes when i am looking for another thing later, then i just happen upon a picture close to something i was trying to find before!
but its good to get familiar with general plant families, that helps. so...say you could look up...its some kind of mustard, cause you see the distinct brassica/mustard flowers.....or some kind of mint type (square stems)...or whatever other clues you can get once you have a few families of plants somewhat down. even with knowing this it is still tricky, i dont know how many times i have tried to figure out an id and not been able to.
the very best way to get going , IMO, is to go on long walks with people who are good at this, and let them point things out, sharing their info as you walk...most people who are into this sort of thing enjoy sharing their knowledge this way =)