Good question. Well, it kind of depends on the mission and the threat. For intelligence work, typically we’re looking at 80% brain power/investigation and 20% technology. So the greatest tool of the trade goes without saying. These tech-centric people coming into power at national-level agencies now are really shooting themselves in the foot. Good analysis is always 80/20, and they’re trying (unsuccessfully) to invert that. The most powerful computer will never out think a dedicated and talented analyst. (Electronic collection faces similar problems – what good is access to 1TB per second if you can’t effectively search and filter through it?)
If we’re talking about prepping for post-SHTF (no internet/power), then I would learn to battletrack using some good topo maps and sheet protectors (use erasable or permanent markers, depending on the pace of operations). Seriously old school analytical tradecraft. On the clear plastic covers, I would mark down and track known trouble locations (robberies, suspicious activity, etc.) and look for any emerging patterns. From there, if I wanted to stop the threat, then Id’ start to draw some conclusions about possible support zones, staging areas, supply, routes, etc. I’d build a ‘pattern of life’ around the threat and start to nail down potential locations for where I think they are. We’d find and kill them eventually but it’s going to take a lot of brain power to make connections from disparate pieces of information. (For instance, if they aren’t driving then they’re bedding down within walking distance.)
As far as analysis is concerned, a good computer where you can store intelligence information is a must (keep that computer offline and remove the wifi card, among other things). If you’re still able to conduct Open Source Intelligence (OSINT) collection, then a secure platform is critical. I’d use something like TAILS (https://tails.boum.org/) while searching and communicating over the net. There’s plausible deniability built in there, which is immensely useful in covering your own ass.
Really, we’re already equipped with the greatest tool (the brain) but it’s all about sharpening that tool and learning how to wield it during combat or security/stability operations.
Does that answer your question? Aside from a computer, or maybe a recording device, there aren’t any better tools.