To get the Student (M1) visa you need to be enrolled on a course of study and have a form I-20 issued by Naples Air Center.
To enroll you will need to pay a deposit. This would be advised by NAC.
Once you have your I-20, you can make an appointment with the American Embassy for the visa.
They will send you all the forms you need. They are also available from the Embassy website. also with the forms is an official paying in slip for the £67 visa fee. If you dont pay the fee, you will be turned down when you turn up. You must pay in on the official paying in slip at a Bank.
Armed with the completed forms D156,157,158 the paying in receipt, the I-20 and the letter saying you will be flying small aircraft you can then attend the US Embassy. Normally you cannot get an appointment in less than 2 weeks of your call.
When you turn up at your appointed time, it takes about 1 hour of queueing just to hand over your papers and then you wait to see a consular official having being given a number.
When I arrived at 10.30, the number called was 35. I was given number 217. There seems little logic in how they call you up. I waited about 40 minutes then out of the blue up came number 217. Three minutes later I was done and on my way out of there.
I have heard stories of people waiting 4 hours. I suppose that it depends on your circumstances and the checks they need to do before they see you. I am male, grey, , 49 with a solid job here and I suppose at little risk of being a terrorist or illegal immigrant.
The Americans are thorough though and you must treat the process with respect. You are asking to be let into their country doing something which the 911 terrorists did, ie train at a south Florida flight school. So no jokes, just go through the process.
Assuming they decide to give you a visa, it takes 10 days for it to be posted on.
Do not try and leave everything to the last minute. If you are going to quibble about some of the incidental costs like visa fees etc, then you might struggle to cover all your training and living expenses.
If you plan to do casual work whilst out there to help out, dont even bother to think about it. Not only do you risk being thrown out of the US and being banned from going there again, you could put at risk the training organisation responsible for you. Being a professional pilot banned from entering the US is not a clever thing.