The conventional wisdom on fencing is that you can't built it too well, and I've found that to be true.
It's also said that you can't have too many gates, or gates that are too wide, and that's true in my experience.
Finally, electric fences are voluntary fencing, and that's why I'm doing this:
My Holstein steer fence
corral/loading chute complex.
The posts are pressure-treated 6x6 posts, buried 36" deep and set in concrete. They are set 8' apart, and the rails are standard 8' lengths of 2x6 painted with preservative. I am careful to set the posts 8' apart because it makes repair of the corral very easy. A board gets broken? Just knock out the ends, buy a replacement 2x6 for $3 and in 10 minutes you're done. They are nailed to the posts with 4 3" nails and an additional 6" spike, two spikes per board. The nails are not enough to keep the board on the posts if you have a cow bounce off the boards; the flex of the impact is enough to pull standard nails. Lag screws are a better way to go, but they are too pricy. 6" spikes are about a nickel each, and for the extra 10 cents, well worth the investment. They also make it harder to knock the boards off from the "wrong" side. Notice that the boards are nailed on the inside of the fence. If you smack the corral from this side, the spikes keep the board on the posts.
Since I'm building stuff, I also put a feeding station into this fenceline; you can see the feeder panel (that green pipe thing on the right side of the photo, laying on the ground).
That's so that the cattle can be fed from outside the corral, for safety and efficiency purposes. I'll put a small concrete slab underneath the feeding area, which also contains a faucet and trough, so that the cattle aren't standing in mud when they're eating. The area around feeding stations and troughs is usually very muddy and I'd like to keep it cleaner from now on.
This area is a dual-purpose. In the non-growing seasons its where the cattle will be kept; close to the front of the property, easy to feed, with an all-weather road and access. It's next to the chute for easy loading in case of flood or other need -- like sales -- and it's big enough that it can be maintained with the big tractor.
In the growing seasons, late spring to early fall around here, I'll have it planted with vegetables. When the cattle return they can glean any leftover plants/vegetables as their first task.
I have found it to be very comforting to be able to put an animal into a secure enclosure and know that it's safe and sound until morning; lets me sleep better.