Upvote:3
First piece of advice: try not to stress too much. It won’t help, and looking stressed and anxious as you await/go through your entry interview might even make things worse by attracting more attention.
Second: prepare well. You may not always be able to use your smartphone during entry into the USA, so gather all your documents together and put them in a plastic folder to keep with you in your carry on luggage:
Third: remember that out of the millions who visit the US every year only a small % are denied entry and generally only the travellers who have had bad experiences on arrival at the border post about them. The main purpose of the entry interview at the border is to rule out any immigration intent by travellers who do not hold an immigrant visa. Typical questions in the entry interview include:
"Why are you visiting the USA?"
"How long are you staying?"
"Where will you be staying?"
"What's your first address in the States?"
"Who are you visiting?"
Answer briefly, accurately, and truthfully (for example “Tourism and visiting a friend”). Produce relevant documents only if asked for them.