An invitation letter can be sent to you by a permanent resident or citizen of the United States. This letter improves your chances of acquiring a visitor's visa to the U.S., among other requirements, because it states a reason of visit, confirmed accommodation during your stay and financial security of you and your host. It is advisable to notarize an invitation letter to authenticate it as a visa application requirement.
Consult your embassy about the necessary details or special attachments that they require your host to include in the invitation letter. This is because different embassies operate differently in accordance to the laws of the governing country.
Inquire if your host is viable to write you an invitation letter. Consider his financial status and government recognition, for example, if he is an approved permanent resident or resident by birth in the U.S.
Contact your host by calling or writing to him, and inform him that you require an invitation letter to help you in your visa application.
Make accommodation arrangements with your host and agree on who will cater for your expenses while in the U.S. If your host intends to cater to your expenses, your embassy may require him to state his financial status or include a bank statement as proof.
Ask your host to write a letter of invitation three to four months prior to your intended visit to give you ample time for the necessary preparations, such as medical tests and passport and visa applications.