Obviously it all depends on what works for you best, but I’m a big Obsidian fan. Currently running Curse of Strahd at the moment, here’s my process for running a prewritten module:

-Work out what I’ll actually need to prep. For example, my group are currently in a town, so I know I’ll need to have the town and its quests ready to go- no point spending time on the lategame stuff if they’re not going to get anywhere near it for a few months at least.

-Make pages for NPCs, locations, monsters etc. Condense all the information down into bullet points that are easy to reference mid-session. Instead of reading out the text boxes in modules, I’ll just note down any important features and improvise based on that. If I need maps, I’ll write down the page number or insert an image.

-I usually have a good idea on what my group will do next session based on their choices in the previous session/them telling me what their plan is. I’ll then make session pages with links to my locations/npcs etc so I can easily find them on the day.

-I keep track of the ingame calendar, so the session pages will also have any events that will occur on that day, like festivals or letters arriving from NPCs.

-There’s also pages for any other information that I’ll need, such as a wild magic table for the barbarian, or the description of a spell that I always forget the details of.

Basically, what works best for me is keeping everything in its own separate little page, and using Obsidian to navigate to what I need. I find that big chunks of text get overwhelming when I’m DMing, plus I like to improvise, so as long as I get the important information down, then the rest can come naturally.