We're planning to spend several thousands on a once-in-a-lifetime trip.
I have a chequered history so we're applying for visa's with full ACRO declarations as we don't want to be refused entry a't the immigration desk'. No 100% guarantee's, they can be quite picky but considering the financial investment I think it's worth the belt & braces approach...
Mine was only a written police caution in 2006 for something silly but now it still shows up on Acro checks and enhanced dbs/crb checks and will show till I am 99 years of age as do all cautions written or verbal now.
First I had to be sure of what visa I wanted, then fill in an online application, sometime later (mine was a few days) you have a long expensive phone call like a triage, they then give you a date to attend the Embassy and a pack arrives with what you have told them before your appointment date.
I had to go to the Embassy in London in 2008 as I was applying for a B1/B2 visa which lasts 10 years and for periods in the states upto 6 months at a time.
No matter what day or time they give you, allow the full day. You queue up outside where the usual hyper security checks happen, you then go and book in and wait in a hall/office waiting room. This may take about 1-5 hours but when you get in you will see why, there is a lot of people going there. I only waited an hour and a half.
Then you get a tannoy call and you go to a semi private off shoot part of the building. Where a man or woman with absolutely no sense of humour and a face so stern she could be in the daily mail sad story, interviews you
They ask why do you want to go to the states, some general info then about the reasons for the acro. ABSOLUTELY be 100% honest here, they already know everything but want to see if you can be trusted.
After the interview they ask you to go and sit down and await a call..it can be 30 mins or a few hours depending on the information. They then call you back and say yay or nay. I only had to wait 20 minutes.
My case was yay so they take your passport off you which then gets sent to their approved visa place (again another charge) and then comes back to you by a special signed for courier within 10-14 working days (check this with them but I remember they do tell you how long if it is a yay)The American visa is bonded into your British Passport.
Going through customs I have never had an issue apart from the usual why have you got a visa?..again the states immigration has had a humour bypass...be polite and explain clearly and you'll be fine, by explaining I mean why a visa and not just a simple etsa like a holiday person. I've probably been stopped no more than twice since 2009.
I hope that helps