So, I'm not a big fan of the default ACKS random encounter tables. The thoroughness of having a full dozen animals for every terrain type is beautiful, but if you're not using every terrain type in your game, or if you'd like a different spread, making a three page chart seems like more prepwork than I'm willing to do.
So here's my own system:
First, roll up a bunch of random encounters that seem interesting and relevant. Make sure to use at least one of these or something like it.
Do this on your own time. So, let's say that we have two dozen random encounters that we like.
Next, we divide the regional map into a handful of large regions. For my map, I'm going "The entire southern half of the map" because that's fairly inhabited and borderlandsy, and then the northern half of the map is divided into "Glacial Plains" and "Awful Tundra."
So, I pick out twelve encounters that seem appropriate for a vaguely civilized area.
1. Todd the Silk Merchant (and friends!)
2. Ladamy, the fugitive.
3. Bestie, the greatest of cows.
4. Bandit Keith and his Knife Bros
5. Bandit Graham and his (nut) Crackers
6. Gajarahajad, and his Questing Knights
7. ROAD TRIP (A pothole damages your wagon/horse.)
8. Snow beetles. (Immature)
9. Oglaf the Panzerbjorn. (Has an urgent need)
10. Carnivorious Deer
12. Patrolling Snow Elves.
The elegant bit, though, is that unbeknownst to YOU, dear reader, the order of this chart was predetermined! I secretly subdivided Borderlands into lesser terrain types, that can be simulated by rolling different dice! So if you're near a village, you roll 1d4 on this chart! If you're on a main road, 1d8! In the forest, 1d12! Then, after the party has an encounter, you just remove it from the table and replace it with another one from the pool. Or, at your discression, leave it on there for a bit. Maybe they'll meet Oglaf again someday.
I'm also proud of including a terrain event on there. It's an easy way to remember to inflict downed bridges, rockslides, and snowstorms on your players.
EDIT: You can also play with modifiers. If they're deep in the forest, you could do 1d4+8 to just limit yourself to the forest encounters. Or 1d8+4 if they're still on the road deep in the forest.