For open book exams, SANS GIAC exams can rank from moderately easy to hard depending on the course you're taking. I have been through two SANS courses in a span of 2 years while working a full-time SOC Engineering job. As a perfectionist, I like building my own index. That way I know what I wrote down, which page I read about it, and how much information is in the index. So, you ask, what's the best way to build an index from scratch? I have a synonym for you: GET.
Get Organized!
Whether you are someone who has a chaotic desk but knows where everything is or someone who has a neat and organized desk, this tip will save you time during the exam. Different bright color bookmarks will save you lots of trouble. I advise that you buy different bright color plastic bookmarks. Make sure you have starkly different color for each book SANS sent you. It is up to your discretion if you want the book for labs organized in its own separate color. I have done both ways: once I used a separate color for the lab book, another time I used the same color for the labs on the corresponding book (i.e: Book 1 is using blue bookmark so the book 1 labs are bookmarked in blue in my lab book).
These were some of the bookmarks I used for my GSOC.
Excel is your best friend!
If you want to excel in your career, Excel is your best friend! Pun intended! I start all my indexes from scratch on Excel. I usually have three columns: Name, Book.Page, and Description/Definition.
For the Book.Page column, I usually my own code such as "2.139", meaning Book 2, Page 139. If the specific information is also on other pages, I add them alongside the first numbers as needed.
Take Notes in the Index as You Go!
If you are a perfectionist like me, you will regret it if you don't. If you are a fast learner and want to revise all the books before the exam, you can take notes in the index whenever.
I love filling out the index as I read through my books. Each presentation slide will usually contain important keyword or information that is testable. I write them down, note the book and page, and fill in the defintion as much as I can without too much verbose. I also fill in the cell for the Book.Page with the same color as the bookmark I am using for that book. While I put on the bookmark, I usually write the page number in sharpie on the colored end. This allows me to see the page number so I can turn to the page easily while under pressure (aka exam time!).
Once you're done with the index, you will see nice colored column with your respective color scheme. It is time for the DJ MIX UP!!! Go ahead and create a table with headers for the whole index. Then, sort the name by ascending order. TA - DA!!! You're ready to print your index out at a FedEx or OfficeMax store. Make sure you send your file over as a PDF after you look through your margins and ensure that it fits the way you want it to on paper. It is recommended to have a back cover and a front screen cover for protection.
Bonne chance in your upcoming GIAC Exam!