If you have a weed in your yard and you do not know what it is the best thing to do is to take it to your local garden center and maybe they can give you a correct id of the plant. If not and you want to post here, here are some points that should be considered so that you will get a response that is reasonable and helpful.

1. If at all possible get a picture of the flowers, including close-ups, and of the whole plant with any special feature such as thorns or hairy leaves as close-ups.
2. Give the height of the plant.
3. Is it herbaceous or woody or woody at the base but herbaceous above?
4. are the leaves sticky or hairy or??
5. what are the growing conditions: in sun, in shade, on sandy soil, on clay soil, in water, ???
6. flowers: color, size, shape (like a sunflower, like a snapdragon, etc.), arranged how (in a spike coming out of the plant, in spikes along the side of the plant, etc.)
7. seeds: have hairs on the seeds, have thorns, in burs, in pods, tiny, one large one, ????

I have only briefly itemized some of the items that are used to identify something that is new. Please take the time to do a good job of describing the plant as this will encourage posts with guesses as to what it may be and just one of those guesses may be the answer. Just saying a green plant with yellow flowers will get no responses other than Are you kidding!!!

Help those who can help you help you!