Hi, I have a UK passport, and travelling with my sister who is a airline crew for four (4) days

Hi, I have a UK passport, and would like to travel with my sister who is going to Peking working (airline crew), it's a four(4) day trip. What documents would I need to submit when I go for a visa at the London office. I have yet to buy my ticket, and will be staying with her at the hotel. Looking forward to your reply