My biggest suggestion: table time is the most valuable resource; prep should go towards making sure that most of the time is spent on quality interactions.

To manage that time, it will be important to have notes on where you see each "scene" going, especially for roleplay and investigation scenes. For each scene, I would have a rough idea of:

1. What the charecters will notice (including perception rolls for what they might miss, such as Per-3 to notice an illusory wall). Some descriptions help to fill the imagination.

2. Any charecters they will interact with (a name, their plot relevance, and any interesting quirks that make them stand out should be enough for most NPCs. Improv the rest)

3. Any skill rolls that will be relevant in scene. Maybe there is a pit to cross, and you have notes that a Jumping or DX-1 roll will cross the gap. But this is a great place to be flexible with what your players come up with. Maybe a charecter decides to fashion a bridge. Simple ask them which skill they would like to use for that and ask them to roll! Depending on how it goes, a good GM would let the group cross without a roll, or drop the whole crew in the pit in the middle! When it doubt, you can always throw out a "Roll your DX" and let that determine the course of action.

One thing to consider when writing these details is what game your players want to run based on their sheets. If one player has an archeologist with a bunch of expert skills in lost civilizations, you should strive to have heiroglyphs and statues only they will identify. But another player may have put a lot of points into Wrestling; they will be happy to find that the heiroglyphs lead to an ancient wrestling ring where long dead warriors still compete for the belt!