Recently I've had the opportunity to read through Caesar's war commentaries, which have undoubtably had quite the impression on many people throughout history. His writing style certainly helped this "Great Man" to become highly aggrandized both in his time and even now. This prospect was obviously not lost upon the man himself, as his writing is unashamedly good at advancing his own positions. As such, this stands out as probably one of the finest works of propaganda documented from the ancient world. Still, as with any good propaganda, there were many lessons and truths to be found there for one reading between the lines (or, of course, to ensare one with partial truths).
The largest thing that stood out to me was the laser like focus he had on attaining his ends and the clear thinking he had on using suitable means to obtain his ends. Though not stated in his book, if you do some searching, you can see that he was aspiring to be his generation's Alexander the Great. Supposedly his realization at the age when Alexander had the world prostrate before him filled him with a great sense of shame for not having achieved the same greatness yet (which pretty much guaranteed megalomania with that as your desired end). Despite what many would consider having a literally insane goal (as many elites thorought history do), he showed remarkable sanity in the pursuit of this goal, actually choosing things to do that would ensure he achieved this goal.
Immediately upon deciding his goal, he did as much as possible to win glory and fame among the people and politicians who wielded the most power. For him, this meant becoming a great general on the military side and a consul on the civilian end of the political spectrum. Both of these goals, like his primary goal, were pursued logically and effectivley. Two examples show this acumen quite clearly.
First, in combat he preferred using the size, ability and technology of the troops he had at his disposal hardly ever for purposes of more than skirmishing, unless conditions favored him winning a "pitched battle" involving the main body of both forces (due to favorable terrain, etc.). Instead, this force was used, much as the Security Services of the Modern State is used today, to induce surrender via hunger and/or terror in his foes before even striking the first blow (note here how I specifically talk here about the Security Services and not the modern conventional armies, which have comported themselves most incompetently for the greater part of the last century continuing to the present day). While there is nothing new here in the theory of warfighting (see Lao Tzu, etc.), it is still an instructive example of what to do in War (and what not to do in Pompey or the Gauls' case).
In regard to becoming a consul, though not touched on terribly much, he was certainly keen enough to ally with those who were from rival factions where their interests intersected, evidenced by the "First Trirumvirate" and mentions of his former bond of marriage to Pompey's relative. This of course, was supplemented by the usual politician stuff, such as liberally spreading favors about to ensure loyalty to him. Later, after crossing the Rubicon, his positioning and constant delagations of peace towards Pompey's faction, though really a cynical ploy preying upon Pompey's hubris, did much to make him look like the "good guy" among both people already inclined towards him and those loyal to Pompey (once they had Caesar's army breathing down their necks). All these things cast the die in favor of him.
Basically the man really knew how power "worked" in society and acted accordingly, to spectacular results. The only hole in his whole plan was inherent to the goal itself, as the only means suitable to achieve his ends were guaranteed to make him powerful enemies and generate blowback for him once his goal was achieved. Indeed, once he achieved his goal (a topic he couldn't write about thanks to Marcus Brutus), he really didn't seem to be able to do anything constructive with it (just like pretty much everyone else whose goal is simply to gain the power, not to use power as a means to some other end).
It should go without saying that the above insights go well with some of the meditations Marcus Aurelius had upon power, as he was in a similar position but had the benefit of time and age to be able to reflect on what brought him success and failure once in a position of power.
Other than the above, there were a few other things of note here, specifically more on how the practices of the time for gaining and maintaining power really haven't changed materially from then to now. The US Empire still demands hostages to blackmail conquered nations into doing our bidding, though it is now done via the security services and the financial sector. If you want to see this in action, then consider the ongoing NSA and CIA spying, coup generation, etc. from basically the foundation of those groups. Also note that pretty much every subservient nation to the US has to keep their gold on deposit with the New York Federal Reserve, which promptly re-hypothecates the gold into Corzine Vapor.
Similarly, his impressions of the Gauls and the nature of man stand out quite clearly, as the Gaulish thirst for freedom was not criticized by Caesar, but instead taken as a given, as men would naturally prefer living according to their own conscience as opposed to Roman slavery (which was frequently the rallying call of the Gauls). At least then the elites were quite open about their aims to enslave the populaces they were invading, which today has to be grotesquely evaded with neologisms like "Humanitarian Intervention" since we now pretend not to be a racist and sexist society of primitive tribalists (except on game day).