While an extraordinary amount of luck is certainly necessary to find high runes, you can still do things to improve your chances (unlike the lottery).
If possible, you should always hunt in areas that can drop Zod. The relative distribution of runes is always the same everywhere (except the Hellforge) - it's not like you increase your chance of Ber by giving up Zod - so long term you're best off shooting for the moon.
Certain monsters drop a higher percentage of runes than others. It is therefore a decent idea to hunt in places where they are. Unfortunately the best candidates are not exactly easy targets. All wraith-type monsters drop runes about twice as often as regular monsters. Wraith types are ghosts, gloams and finger-mages. The only one of that lot that are at all easy are the finger-mages (found in Act IV).
Next best are Cows. Cows drop runes about 50% more often than regular monsters. And Hell cows can drop Zod. But, you have to finish the game to get there and not every build can kill cows quickly.
The other "monster" that is good for runes is chests. Proportionally, they drop about 50% more runes than regular monsters too, although chest drops are a bit more complicated than monster drops. Plus they don't need to be killed
Another thing to bear in mind is that boss monsters don't actually give up that many runes. It's the little guys that your runes will probably come from. A side-effect of this is that it is better to kill in full games than solo, if your build can do that. Doesn't affect the boss drops but it means a lot more drops from the normal monsters.
Last of all, the
rate at which you kill is about the most important factor really. The number of runes you get per hour is roughly (kills per hour) * (runes per kill). The advice above is all about improving the second factor, but you can probably make as much of a difference to the first factor. It's no good killing the best monsters (cows, wraiths) if it takes you forever to kill them. So finding a place that your char can really slaughter lots of regular monsters quickly is also good.
Anyway, that's the basics. Some possible locations are Hell Cows (Zod, lots of monsters, good rune rate); RoF/CS (Zod, good rune rate); Pit (Zod, easy monsters); Lower Kurast (only Ber, but lots and lots of chests).