A fiance visa is fairly straight forward. You should check if you meet the following as the more evidence you have the easier it will be to succeed.
1) How long have you been in a relationship.
2) Do you have evidence of this. Records of skype chat, photos, plane tickets.
3) Have you ever lived together in a marriage type relationship. Your friend could visit you on holiday and return. Do not mention fiance or marriage on general visitor visa application or on arrival in the UK. Preferable apply for a month, but stay for 6. Do not overstay.
4) Do you earn 18600 pounds annually. 6 months orginal bank statements and payslips. Tax P60.
5) Do you have adequate accommodation. Tenancy agreement or mortgage statements. Overcrowding will result in a refusal.
6) Pay a solicitor to write a letter showing you will sponsor your fiance.
7) Write letters on your intentions.
Organise a wedding venue and pay a deposit.
9) Organise for a Council to conduct the wedding ceremony.
10) Your fiance must apply for the visa from their home county. A general visitor visa cannot be converted from within the UK.
11) Fiance must pass an English Test. It is thought this may be at Level B1 from October 2013.
12 ) Check if TB testing must be done in fiances home country.
13) Make sure there is no overstaying as this results in automatic refusals.
14) Read the UKBA website for guidance as rules change all the time.
15) make sure fiance has no criminal records as this could result in a refusal.
16) Fiance cannot work until married and applied for FLR. Best method is book an appointment as the postal method can take 6 months or longer.
17) Once fiance has visa add their name to the Council Tax. This is good evidence to show to marriage councillor for proof UK address.
18) Change a utility bill once married into your spouse to show as extra evidence spouse living with you at UK address. This is needed for FLR applications.
19) Take loads of photos at wedding and submit for FLR application. 2 guests at a wedding is not enough and won't look genuine.