Hello!
*What is the best way to know the value of ant banknote?
*I also would like to know that which points we should consider before buying any banknote?

I thank you in advance for your attention on my questions.

Hello,

To know the prices of banknotes you have several solutions :

1/ See the "World Paper Money" which is the "bible" for all the banknotes collectors all aroud the world

2/ Ask some collectors

3/ look at the auctions on a website like delcampe and you will find a lot of banknotes and a lot of sellers. You have a good idea of the prices

The most important thing for banknotes is its quality. Except for very old or very rare banknotes the UNCIRCULATED banknotes; those which are never been in circulation are the best quality.
You will see some exemples on Delcampe site.

Sincerely

Jean Pierre