There are a lot of ways to proposesomeone you truly love. Before going into this, I will advise that you develop a strong friendship with someone you want to propose to, to the point it will be difficult for such a person to turn down your proposal.
You can propose to the person you claim you love by getting a beautiful place that will actually draw people's attention to you. A lot of people will really like it, especially if you go about it in a romantic way. Get a photographer; I'm pretty sure you'll always want to remember that day forever. If you are proposing to a girl, it is more of a tradition that you must be on your knees when proposing to her. You can also seize an occasion to propose to your partner. You can take your partner to a party, and arrange a deal with whoever is performing at the party without the knowledge of your partner, let it be a surprise; you can arrange a band, an artist to do this for you.
Overtime I have heard about a lot of proposals being turned down due to the poor approach people go about proposing their feelings to their loved ones. The first thing you need to know is that every proposal you are willing to make to someone you love should be based on love. If there is no emotional link between the two of you, don't even try and propose to her. A sincere relationship should start by knowing each other. You start this with friendship, this will give you the chance to each other better and both of you will be more connected emotionally. Try every possible means to know a lot of things about the person you claim you love.
Most girls will naturally accept your proposal when they are amazed about the manner you seem to know some things about them. Another thing is to be sure of her feelings towards you. Let her see you as someone she can confide in. And most importantly, give your friendship the quality time it deserves. Finally, if you can diligently follow everything I've stated, she won't have any other choice than to say yes when you finally propose.