It is very common for two friends/best friends to fall in love or fancy each other after being friends for quite a long time. Knowing what your crush's hobbies, interests and turn-offs are will boost your chances of becoming their partner.  Try talking to them as a friend first. If you approach the person as a crush, they will only see you as someone who likes them. This could potentially be problematic if they don't like you because they will be less likely to want to get to know you. Become friends first, and then later try to pursue them. Make sure they feel comfortable around you, through communication. Get to know them and let them know you (what you like, what you don't like....etc.) This determines whether you are compatible or not. Hang out with the crush. Not one-on-one yet, but maybe ask your crush and one or two other friends to go to the park or come over to play video games or something. This way, you can see and interact with each other in a more natural environment.  Do activities together. The more you interact, the more they'll think of you. It's a no-brainer! Eventually, you could ask the crush if they wanted to do something casual with you one-on-one. Maybe it's a sport or a movie. Figure out what interests the crush and ease into the suggestion. Apart from having an unhappy or forced relationship, pushing things too fast could also ruin the bond you've already created, which could lead to losing them as a friend as well. Be patient!  Clinging is one of the things people dislike most in a relationship. Give your crush their space, and let any relationship unfold at a natural pace. Do not stalk the person. Not only is this inappropriate, but it can be illegal – and it doesn't work. Do not flirt uncontrollably with the crush. Do not make sure you hear everything about this person, either. Don't try to be around the crush constantly. If they ever did like you, this will put them off. Hang out together, have fun and talk. If it's meant to be, it'll happen. If not, there are plenty of other fish...

How would you rephrase that briefly using Vietnamese?
Xây dựng tình bạn với họ và xuất hiện bên họ nhiều hơn. Dành nhiều thời gian với họ hơn. Đừng vội đi quá nhanh và quá xa. Hãy là người họ có thể nương tựa. Tìm hiểu về sở thích của đối phương.