Ask HN: How should I register my business

My friend and I have been working as independent energy consultants for about a year now and we are planning to incorporate to be able to extend our services. We both got our PhDs last year and we want to eventually make a research facility that can develop and sell new technologies.

My quick question is that in order to register our company what should we do. And what type of company should we register in order to be able to easily expand it.