Often I hear people say " I was denied a visa"; even when they seemingly have fulfilled all requirements to acquire one.

What are the things we should know, or have; or do in advance ahead of preparing for graduate studies in the USA?

i dont want to spoil your mind or anything, but at the US embassy, it God oooo, because they dont really care about your documents,

Getting your F1 visa is 50% luck but its also 50% preparation. Some things can enhance your chances of getting a visa. One is the school you're going to. Someone going to Harvard for instance is 1000% more likely to get a visa than someone who gets admitted to a community college somewhere. Second is finances. If you cannot clearly show that you have the money (and by this i mean you or your parents, not your sister's friend's uncle's stepbrother) for your education, your chances also diminish. If you have a scholarship it helps your chances as well. The third factor is you as an individual. How intelligently do you answer questions? Be prepared to answer questions like why did you pick the school you're going to? Why that course of study? What is your goal after school? (And please don't say you want to remain in the US to work. Even if that is your intention, tell them you intend to come back and work in Nigeria). One other thing, if you've travelled before, especially to the US, you are more likely to get a visa. Hope this helps.

Consultant, na you biko! abeg set up a clinic fast for those kids that require F1 visas.

Truth, getting a visa requires a good deal of prayers cos some kid might wake up on the wrong side of bed and deny every soul a visa.

School type helps, ensure you pick a well recognised school in the US, your course of study is also important, don't expect a visa if you are going for a masters degree in history or political science or religious studies, you are likely to be told you could just easily study such in nigeria!
Be bold at the interview, jittery people are likely to bungle every simple question they are assked. If you have travelled and returned before it helps you a great deal (it did in my case, i was not asked all those stupid ques and i got out faster than everyone else).

Thanks guys. I'll keep all this in mind.

About the previous travel experience? Does it help in my case that I was in the UK for three and a half years during my primary school education in early '90's?

Rare:

Thanks guys. I'll keep all this in mind.

About the previous travel experience? Does it help in my case that I was in the UK for three and a half years during my primary school education in early '90's?

Did you overstay your visa? If not DO NOT USE THAT PASSPORT! Get a new one!