While proposing a girl you should show her your presence irrespective of the surroundings. Make a complete focus on her. During a proposal be with her like that she felt you are the only one who care for her. Your body language has to be confident and suggestive. She must felt that you have a desire towards her. When she gets such feelings from you she will definitely accept your proposal.
These tips to propose a girl will surely work and make your proposal perfect. Just give them a try. Here are some talks on Quora that will also help you what people think about proposing a girl.