First question you need to answer is guns, melee, or both? Both tends to be more dangerous and less efficient than picking one or the other, but it can certainly be done.
For gun only bases, its beneficial to have a long-ish straight path level with the player, that lets you just sit and pop headshot after headshot as they run straight to you. I like poles for this, not a full width block. Ideally you have a way to push them off a ledge or whatever when they get close to you, forcing them to start over and keeping you basically 100% safe. Sledges work pretty well, sitting off to the side facing the end of the pole. Not perfect but good. No other traps are really necessary though an electric fence to slow them down at points along the path is nice, too.
For a melee base, electric fences are practically necessary. Keep in mind, zombies only get zapped by the fence as they enter the space the fence line occupies, and never again unless they leave. You can use the activation delay blocks with a camera to force the fence to cycle on and off every 1s or so, creating continuous shocking. Run that against a 2-thick barrier made of differing height edge poles back-to-back. This gives you a 2 block barrier they must break through, even though the physical distance is less than 1 meter.
Nearly every "amazing" horde base incorporates one or both of two important block types to exploit the zombie AI.
First, are blocks that zombies see as a path, but are not actually capable of being crossed. This causes them to run off the edge like Wile E Coyote chasing the roadrunner, before plummeting to the ground and starting over. A good example of this are half wedge tips facing downward, and then covered by half blocks. Put this at the end of your path for about 3 blocks before where you stand and zeds will repeatedly run off.
Second, are blocks that zombies don't see as a path, but are possible for the player to cross. This lets you force the AI to not go places you don't want them to, and redirect them to your preferred choke point. There are tons of these, but my favorite one is a doorway placed on its side. You can make a 2-block gap, fill it with a sideways door and, even while shut, the zombies will ignore it as not a valid path. This lets you create simple fallback positions when things go sideways. For a melee base, behind your wall of poles, the player can stand on a door. if the block breaks, simply back up a few steps and they'll start looking for a new path to you. If you have a long wall, several doors side-by-side give you several standing points you can switch between as blocks break. Start at the left or right, and work horizontally through horde night as blocks break.
Keep in mind zombies do their best to get to you first through a valid path, and second as close as they can get w/o a valid path. In v1.0 I believe they changed the weighting to prefer horizontal closeness over vertical. Meaning given a choice between getting 2 blocks under you vs 2 blocks sideways to you, they'll go under you first and try to break blocks to create the path. I haven't done any testing on this, though, its anecdotal. What this means it, build higher and let them get horizontally closer. If you're only 3 blocks off the ground, they're more likely to break out your supports than come up your ladder to a disconnected platform.
Edit: Spellings