As you can see from the many posts and threads in the forum (such as this fiancee-visa-questions-t29484.html) concerning this question - it is a common struggle to figure out what exactly you need.

The Guide to London includes information about finding work, visas, and more. There is also a FAQ section that addresses the different visas you may be interested in: http://www.easyexpat.com/en/faq/departure.htm. We also recently posted an article on obtaining a visa to live, study, work in the UK. And of course the UK Border Agency is the best official source of info: http://www.ukba.homeoffice.gov.uk/

Some great resources to work through! But in specific answer to your questions:
Your best option is to get a fiancee or marriage visa, as a work visa can be quite difficult to get depending on your qualifications.

"If you do not qualify for a Tier 4 visa or EEA Family permit, you must apply for a visa to work within the UK. Visas are assigned by a points assessment system designated into tiers. Each tier includes several categories of workers; each category within a tier has specific visa requirements, and supporting documentation you must submit along with your visa application varies. Depending on the category under which you apply, you may be required to apply for a visa before you enter the UK, or you may be allowed to apply if you are legally present in the UK.

Under most points-based visa categories, you must have a job offer or work assignment in hand to be eligible to apply for a visa. Your job offer must comply with government regulations, including minimum wages where applicable."

UK Fiance Visa Requirements:
The sponsor and the applicant must intend to get married within a six month period.
They must have met each other.
They must intend to live together permanently.
The applicant must be able to support him / herself, or be supported by their partner, without access to public funds.
There must be adequate accommodation in place.
There is no requirement that the applicant and the sponsor have lived together before applying.

Successful applicants receive a 6 month visa in which to come to the UK and get married. They are not allowed to work while on this visa. Once married, the recipients must apply for a marriage visa.

UK Marriage Visa Requirements:
The sponsor and the applicant must be legally married or in a civil partnership
They must have met each other
They must intend to live together
The applicant must be able to support him / herself, or be supported by their partner, without access to public funds
There must be adequate accommodation in place

Once the visa is obtained, (if the marriage is less than 4 years old) there will be given a 2 year visa to live and work in the UK or or (if Applicants who have been married and lived together for 4 years or more) they may be granted Indefinite Leave to Remain.

Hopefully this info helps you get started. Anyone else have personal tips to share?

 

Nearly. You can apply for her to come here as a fiancee and marry in the UK, then apply for further leave as a spouse. Or you can travel to the US, marry her there, and then apply for a spouse visa from the USA. The third option is for her to enter as a 'marriage visitor' and then return to the US to apply for the spouse visa.

If she comes to the UK on a Tier 2 (Intra Company Transfer) visa then she would be free to marry you. She would also be allowed to apply for further leave in the spouse category ("switching") from a Tier 2 visa. In this scenario, it would be sorting out the Tier 2 visa which would be the complicated area!

From the USA, she would apply (online is easiest) and then book a biometric enrolment appointment at her nearest Visa Application Centre - there is at least one in every state. The local centre then takes her fingerprints etc, then either they send the application to New York or they tell you to do it, with the biometrics inside too. It takes about 3 days for New York to deal with it, then it comes back to you. It is not possible to have it dealt with the same day - although I believe you can pay a premium for a next-day decision.

Have a look at this post here which takes you through the specified evidence. The minimum income requirement for a fiancee is that you are earning £18,600 (or can show specified savings).

She would be entitled to use the NHS and can register with your local GP.

 

That's all you need to actually *get married* - even an illegal entrant can get married in the UK, you just need to show you're living here.

To get *into the country* you need to get the visa sorted. (assuming your fiancee doesn't want to smuggle herself into the UK, ha ha. Which is needless to say a really bad idea.)

Do you want to marry in the UK or in the US? If you plan for her to come here then get married, then you need to apply for the fiancee visa - and do it soon. If you plan to marry in the US, then you can do that whenever you like, then apply for the spouse visa.

If she gets a fiancee visa, then you need to marry within six months, then apply for the spouse visa. No need for her to leave the UK.