The question here is really how to do you structure your math! There is no difference between the online and the in-person experience here.
First: Use tables for multi-dimensional data
If the interviewer gives you linear data, you can simply jot it down on the LHS. However, if they say, for example "We have 4 main costs", you better be setting up a table ASAP! Those 4 costs will be your rows, and any additional information given will be in each respective column.
Not only will this help you write down all of the information quickly AND keep track of it, but it will help you figure out where to go next!
By the way, the same applies for exhibits. Write down the key information back onto your sheet!
Organize all of your notes in a casing template
1) A seperate sheet for each "portion" of the case...with clear locations + methods for title/subject, notes, calculations, takeaways, etc.
2) Figuring out a location for everything and where each information type should go
3) Seperate sheet for math calculations
Third: Learn to quickly take notes down
1) Decide physical vs virtual - are you a faster typer or writer?
2) If virtual, pick the best tool - try outlook draft emails (so you can store/organize with your email), try notepad, try a tablet so you can write on it, etc....find the one that works for you
3) Only write down what is important - you should know this! You don't need to capture everything. Just like in a case, figuring out what information is not needed is just as valuable as figuring out what information is needed.
4) And then, what you do write down, write it in shorthand!
I.e. If I say "Your client is Bills Bottles. They earn $800M in profits each year by manufacturing bottles to soda companies in the US and Europe. Over the past two years they've seen profits falling and have brought you in to investigate"
You should write:
- Bills Bottles
- Client = soda comp
- 800M P
- P [down arrow] 2 yrs
- US + Europe
- Obj: Fix P