1. Valid Passport: You will need a valid passport with at least six months’ validity beyond your intended stay in the UK. Your passport should have at least one blank page for the visa sticker.
2. Visa Application Form: Complete the online visa application form, which is usually available on the official website of the UK government.
3. Passport-sized Photos: Provide two recent passport-sized photos that meet the specific requirements set by the UK embassy or consulate.
4. Proof of Travel: Provide evidence of your travel arrangements, such as flight tickets or a detailed itinerary showing your planned entry and exit dates from the UK.
5. Accommodation Details: Provide proof of accommodation arrangements during your stay in the UK. This can include hotel reservations, a letter of invitation if you are staying with a friend or family member, or other supporting documents.
6. Tuberculosis (TB) Test: Depending on your country of residence, you may be required to undergo a tuberculosis (TB) test and provide a certificate if you are staying in the UK for more than six months or if you are applying for a visa from certain countries.
7. Additional Documents: Depending on your specific circumstances, you may need to provide additional documents, such as proof of employment, bank statements, a letter of invitation, or other supporting documents as deemed necessary by the UK embassy or consulate.

The standard visitor visa for tourism purposes usually allows for a stay of up to 6 months in the UK. However, the duration can vary depending on the specific visa type and the discretion of the immigration officer at the port of entry.

The processing time for a UK tourist visa can vary depending on several factors, including the country from which you are applying and the time of year. In general, the UK Visas and Immigration (UKVI) aims to process most non-settlement visa applications within 15 working days.