what are some basic points to write about in the 'why us' of a school

Try to get more specific. Talk about things that are directly related to your interests and what resources there will help you further your education, like if there's a course that you're excited to take, or a professor you'd like to research with/learn from. You could also include things like extracurriculars. Just try to make it detailed with things that could not be found from a quick look at the college website, and make sure that you include how you would fit into the college environment well.

If it has good programs/insitutions having to do with your major/interests specifically mention them. Research clubs, activities etc. Talk about how certain aspects of the school personally relate to you and how you can benefit and maybe contribute to them. Basically just do not write about general things a lot of a schools have. Specify what you like about the academics, or extracurriculars, environment, campus etc.

Try to talk about why you want to get in to that particular college.

Your reasons of choosing that college out of so many.

Why you think that college will be the best option for your higher education.

Look up more information about the college and try to incorporate that into your essay.

Perhaps, you one of the professors there is your role model.