If you are born in a visa waiver country, you can normally travel upto 90 days to the USA as a visitor.
You need to apply for a visa beforehand through the ESTA application. You can find info on the website of your local US Embassy.
If you have eever been denied entry, been denied a visa or overstayed, you need
to apply for a visa at the nearest embassy/ consulate.
If you are from a non- visa waiver country, you also need to apply for a visitor visa at the nearest US embassy. There will be guidelines at their webpages.
It is recommended to buy travel
insurance before you leave. It will cover delays, baggage loss, health issues etc. Please check for good deals!
No vaccinations are needed or necessary in order to visit the US.