I still haven't finished editing the accompanying video, so here is the text of the short version of my guide which will be posted in full somewhere on this forum soon...
First check Inara for the material you are looking for. Inara will state certain criteria for the best chance to find the material. This usually includes a system state and possibly an allegiance.
Take CDCs (Core Dynamics Composites) for our first example. Inara says they are found from ship salvage of combat ships, found in HGE USSes, and a higher chance in Federal Boom systems.
One of the reasons I chose CDCs as the first example is because of that 'Boom' thing. Yes, the boom state is supposed to spawn CDCs, however, the boom state more frequently spawns HGEs containing PRAs (Proto Radiolic Alloys), PHRs (Proto Heat Radiators) and PLAs (Proto Light Alloys).
Therefore, you must consider the level of dilution and other circumstances that might cause frustration of finding HGEs, but not the right materials in them.
In the case of CDCs, you can dramatically increase your yield by going to a Federation system in a state of 'None'. This is because a Federal system in a state of none, can ONLY spawn CDCs and Proprietary Composites, so every HGE will contain a variation of those.
Now, once you've identified the best states/allegiances to look for, the next criteria is population, and playing a much smaller role, economy type.
Many believe that high population increases the spawn rate of HGEs. This is not entirely accurate, Mr President. High population increases the USS spawn chance in general, so naturally, more USSes gives the illusion of more HGEs, but I do not believe there is a direct relationship. OF course that still means that high population systems are better for farming HGEs, simply because of a higher rate of USSes.
This is somewhat muddied by the fact that you can often find HGEs aplenty in lower population systems, which brings me to economy. It does seem to be the case that High Tech and Industrial economies particularly, spawn more HGEs per USS, however, again this is a red herring, as I've farmed untold HGEs from Agri and REfinery systems (take Sol for example, it's Refinery/Tourism, and you will never be short of HGEs, I believe this is simply because of the MASSIVE population.
Therefore, the (I admit it's still weak evidentially) conclusion is that if the population is huge (billions), then it doesn't really matter what the economy is, but if the population is only a few million, then economy might play a larger role (particularly High Tech) concerning the quantity of USS and/or HGE spawns.
The actual technique to get an HGE to pop, is very simple, and very reliable. It is an easier technique to use in a system with only one star, but it does work on systems with two or more, provided you follow the rules carefully (and it's not always obvious how these rules translate to complicatedly laid-out systems, such as Sesuang, which has two stars and THREE different orbital planes for the bodies in the system).
Drop into the chosen system. Have orbital lines ON, and take a quick look around, so you can orient yourself with the orbital plane. Now point your ship 90 degrees straight up away from the star, so that the orbital rings and the star are getting smaller and smaller behind you. KEEP THE STAR TARGETED, so you can see how far away you are, and for purposes of orientation (this will be much clearer when I upload the video), until you reach about 2000ls 'above' the orbital plane. Now you want to level off and simply fly large circles around the star which is now way below you, kinda like a fly circling a plate of food, or a vulture circling a carcass, and you STAY between 1700 and 2000ls distant, flying at between 20 and 30c, and you wait for USSes.
If you get 5 USSes in a row that are not HGEs, either drop throttle to zero and drop into normal space, then return to supercruise to reset the instance, or log off and back on again. It's worth doing this in SOLO (or PG), because if you do it in Open, you may be matched in the supercruise instance with another player, which means that when you drop and re-enter supercruise, the instance will NOT reset, because you just joined the same instance as the other player again (which is persistent from the other player's point of view).
I hope this helps, and like I say I have a vid and a more detailed body of text incoming to serve as a guide for all forum users. I have already verified the effectiveness of this technique in 3.0, I have had no trouble getting HGEs with the goods I want. There are other techniques that work just as well, but I have never found one that works better, and I am 100% confident in this advice to both old and new players. I'ts something I've spent a lot of time observing. Good luck!!
