If you are a first timer buying a Hermès Kelly or Hermès Birkin you will need to learn many things related to the bags.
The first one you probably already know is that there is a waiting list to buy directly from Hermès and it might take years to get one so more than likely you will be buying one in the secondary market.
You will need to know the differences between the two coveted bags, one of the most important being the fact that one is a handbag with one handle and the option of a strap (the Kelly) and the other is a tote bag (the Birkin).
Once you know which one is for you, you will need to know the sizes available for each type. The Kelly will range from small wallets and clutches to huge travel bags, and the Birkin will range from tiny collectible versions to very big travel bags.
Next is the materials available, from a huge list of leathers offered by Hermès to synthetic and exotic materials, then there is the hardware to choose.
Hermès offers a gigantic list of colors to choose from and most of them are named in French, so that part will be important to know as well.
The authenticity will be one of the most important aspects to know, who to buy from and issues like the date stamps.
And of course some education about how to properly take care of such an expensive item, because learning how to care prior to buying can actually help you in deciding what is the best material for your specific needs.
All these aspects are very well covered in these two pages:
Kelly Bag Buying Guide and Birkin Bag Buying Guide
They are definitely a great starting point in your quest for your Kelly or Birkin.