If I've been in America for 90 days - it is stipulated NO WHERE how long I am supposed to be home for. Does anyone have advice/experience on how long is suggested. I've heard; stay out as long as you've been in, but could we get away with 2 months away from each other before I am back? I spoke to the embassy and they were absolutely no help. All the FAQ on the CBP websites do not touch this question.
I don't know of any official rules, but I've always been advised to spend at least as much time outside the US as you did inside the US.
So, if you stayed for 90 days, you should really wait 90 days before returning. You might be okay with only waiting 2 months, but you may get questioned further and you risk them not believing you are a genuine visitor and refusing you entry.
Also, I have read somewhere that only 6/12 months can be spent in America. Is this also true AND when do these 12 months start? At the beginning of a new year or when you first travel to America?
For visiting the UK, it's no more than 6 months in a rolling 12-month period, so it may be the same for the US.
I would imagine the 6 months comes from spending as much time out of the US as in the US. If you had 90 days in the US, then 90 days in the UK, then 90 days in the US etc., that would be 6 months out of 12 months in the US.
Finally... I know there are lots of horror stories on the internet and you should not always trust what you read, but I once read that if you got turned around at the border and not allowed into the country - you will not be able to enter that country again for 5 years. Is this true?
Not necessarily - it would depend on if you were issued with a ban or not.
Usually if you get turned around at the border, you then have to apply for a visa to enter the US for the rest of your life.
A visa costs about $140, and you have to go for an in-person interview at the US Embassy in London. It can take about 4 hours for the appointment (lots of waiting around) and sometimes there is a waiting list of a few weeks to get an appointment. On the plus side, the visa can be issued for up to 10 years, allowing a 6-month stay each time you enter.
I have applied for 4 US visas in the past - 2 student visas and 2 visitor visa (I currently have a 10-year visitor visa). Each one took 2-4 months to get and cost a couple of hundred pounds for the whole process. I currently have a 10-year visitor visa, valid until 2020, so I don't have to worry about visas for the US for the next few years.
However, I would give anything not to have to have a visa for the US. You should only try to apply for one if you are no longer eligible to fly without a visa (i.e. if you get refused entry and turned around at the border). The only reason I have one is due to a driving conviction - when I got my second student visa, the US Embassy told me I would not be allowed to enter the US without a visa from then on.
I'm currently working approx 22 hours a week as a waitress in a tapas bar and still live with my parents. I know this does not work in my favour for having many ties in the UK. 
If you can show your employment and that your employer is giving you time off to visit the US, and is expecting you back at work afterwards, then this shouldn't be an issue.
If you can show some evidence of living with parents, then this may help.
Basically, you want to be able to show as much evidence as you can that you will definitely leave the US within 90 days.
