Under my friend's guide (who has a lot of experience applying for visas) I spent time visiting the UK Border Agency website and applied online first. I read and answer questions carefully and honestly. If I had difficulties I stopped and asked for help. And my application online was accepted. I had to make an appointment with the visa section of the UK Embassy in Hanoi a week later. Within 1 week I prepared necessary documents to submit. Thanks to the Internet, I could find out easily where to have my documents translated into English and certified. I thought it was a difficult week for me. :-) But it gave me a new experience. On Thursday I went to the Embassy. They asked me to submit the copy of the family book with translation and certification. I knew it in advance but I got the book just on Wed evening (not enough time for me). I accepted to get back one more time with the book. The staff also advised me to write a letter expressing in detail my purpose to London. The deadline was by 4 pm. I came back home. On the way, I dropped by the translation and I arranged to get the book by 2.30 pm. When I got home I wrote the letter. I thought no more worry when I got back to the Embassy at 3 pm with all the necessary documents. But the next morning when I was in classroom the visa section called me and advised me to change the time to visit London. She said my planned time was too far (over 4 months) and the UK just issued visas 3 months before my departure but it will be valid for 6 months (my planned time still within their permission). That meant I had to change my hotel booking and time in my letter. I could not do that at university because power was off. It was OK with the deadline they said 1 pm on Friday. We still taught but I knew we could go home earlier than usual because of no power. I still felt happy. That deadline I could meet. I stopped teaching at 10 and went back to the staff room to return the class file. Suddenly I was kidnapped to a meeting. I could not refuse. Although sitting in the meeting I felt as if I was on fire. Finally it finished at 11. I rushed home and changed hotel booking and letter and emailed them to the visa section. At 12.30 I rushed back to university to attend another meeting. What a day for me ;-).
As far as I read on the Internet, applying for a visa like my own situation was often not successful (travelling alone as a tourist). I told my friend that I hoped I would get the visa but not too upset if I would not for the first time. What I get from this is a life experience. If I failed I would know what to do to succeed for the next time.
When my visa work finished last Friday, I felt relieved. And within a week I got the Visa, and I felt so happy.
Just have good preparation, just open to other people's experience and advice and open to new things in life plus your little braveness, you can do what you think is impossible for you.