im an american going to england for 6 months...

I've never been to the UK myself, but in my travels to all sorts of other countries it's behooved me to look up their requirements on the various websites their governments maintain for this exact reason.

http://www.ukba.homeoffice.gov.uk/

Here's the one you want. You can click on 'Do I need a Visa?' below, answer a few questions, and get the answer you need.

As for working, I always obey the laws when I can in a foreign country (some of the places I've been to the laws are pretty shady, not the case here for you). My first inclination is to do everything you need to do to be legal and make your visit there as worry-free as possible.

so basically i dont need a visa if im only going to be there for 6 months? and thoses that they even really question are those with a criminal record?

Go to that website and follow the questionnaire, it will tell you if you need a visa or not. My guess is if you're going to be there for half a year then you will need a visa of some sort.

Ok, so since I'm on lunch break and am curious anyway, I plugged in 'living in US, visiting UK'

All foreign visitors who are not European Union citizens need a visa to enter the United Kingdom. Citizens of certain countries can just turn up at the UK border (the immigration desk at the airport usually) and apply verbally for a tourist visa. This can be for a period of up to 6 months. There is no automatic entitlement to a six month stay.

If a visa is granted you get a stamp in your passport showing the length of stay you have been granted. The Immigration Officer can ask any questions he or she likes to determine if the visit is genuine.

It's not just people with criminal records they are looking for. Statistically one of the biggest targets is young single American women. They will be looking for signs that the visitor is not intending to return to their home country, that they are planning to work, things like that. Without a work permit (very hard to get) any work, paid or unpaid is illegal.

They can give a tough grilling, and detain you while they check out your story. They will be especially suspicious if you don't have a return ticket, or ties to your home country such as a checkable job and home address.

While you are detained they can open your baggage and look for diaries, laptops, letters, stuff like that. They can check your phone and any social networking sites like Facebook that you belong to. If you tell them you are in Britain to look at castles or stay with a "friend" and they find stuff like "Goodbye USA! I'm moving to England to work in a bar and live with my boyfriend!" on your Facebook page or in your diary or your phone messages, you will be "bounced". Or if they call that "friend" and he says he's your boyfriend.

Being bounced means you will be held in a custody suite in the airport and put on the next available plane back to your homeland. This will happen even if you cry or threaten to write your Congressman or tell them they can't do it because you are American. Also if they find you were lying then you can get a 10 year ban from the country for using deception to attempt to enter the country.

A problem seems to be that many young visitors don't really see making up a story to tell the Immigration Officer as lying. They sort of feel that it's OK, that a few little white lies are OK. Especially if they are in "love" with some guy with a British accent they met online. That attitude will get you put in a room to cry with a lot of pissed off people from around the world including crazy people, criminals, etc, while they process your flight back. If you have a return ticket they will use that, if not, they will return you and bill you for the flight. After that you will have to repay the cost before they even think about letting you in, and in future you'll have to apply for entry clearance at a British Embassy or Consulate before traveling.

Working "under the table" is a crime. If this is your attitude, they will pick up on at once. They are very very good.

Also you need to have enough provable funds to support yourself for the whole of your stay.

I'm pretty sure I didn't have to have a visa. Mind you, as a Canadian we are part the commonwealth. But I can attest to the grilling...
I got it in London and Dublin. Even though I was staying with relatives and had a return ticket for two weeks hence.
It's a dumb idea to lie, regardless of what border you are trying to cross. Working under the table in most countries is nothing but a world of hurt...

The stamp in your passport is your visa. Citizens of certain countries don't need to apply in advance, that's all.

Correction: visa-free access to the UK for up to 6 months is available to citizens of certain countries who can apply for "leave to enter" at the border.

She's going to Liverpool remember. There's not much work in the first place.