Using your numbering...
1 - No, this won't help. Why would you buy an expensive plane ticket for a trip which you might not be able to take if your visa is refused? I didn't buy a plane ticket in advance of my visa application and my application was approved.
2 - I don't know what a "British Demand Draft" is. You need to show proof of funds, yes. This is usually in the form of either 3 months bank statements (to prove the money has existed and belonged to you for some time, and not that it is money you have borrowed from a friend or family member just for the visa application to be approved), or credit card statements showing access to the same amount of funds.
3 - Know more about the UK? You didn't state what country you are applying from, but most countries all you do is sumit a form. Nowhere on this form does it mention anything about knowing UK general knowledge. If you have to attend an interview in person for your visa though, this would certainly be advantageous. Wouldn't you like to do this for yourself anyway, to learn more about the country you will be living, working and holidaying in for a year or more?
4 - Again, booking or paying for these travel plans is not required. But certainly have some idea of where you will stay and what you'd like to do and see while you're here. I had a rough idea in my head when I applied but I didn't have anything booked.
5 - Once more, this is certainly advantageous for your holiday plans but won't have anything to do with your visa application. The British Consulate at which you apply will not expect you to be staying in YHA hostels, many travellers prefer hotels or independant hostels. I don't think this in itself will affect your application.
Certainly none of these things will ensure your visa. #2 will definately be an important part of getting your visa approved, but again it won't guarantee it.
More importantly you mentioned you are married with a child. You do understand that for your visa application to be successful your husband will need to be eligible for a WHV as well, and plan to take his at the same time as you?
Have you read the
Guidance notes??? They will tell you all you need to know.
