I've got two kinds of redstone-operated gates.



This one is the vertical door. You need to begin with a 5 x 5 x 1 hole in the ground. The wiring is the same on both sides, except one has that tower coming up. There are two sticky pistons that act as a gate and the pressure plates will deactivate them and allow you to cross. If you cross too slowly or if you pass the pressure plate too quickly, the gate will crush you. After, you just cover everything up and voila, a gate!

The other one is a little more complicated.

First, you need to begin with this frame.



Next, the back of your frame should look like this.


Note that you only put blocks on the top two rows. It's crucial that this frame is like this, otherwise the redstone will not be correct.

The front should look like this.


Now, you should put in some sticky pistons. You'll need 12 in total. Four of them will be facing perpendicular from the door and two will be facing the door. This will cause the back sticky pistons to push the forward sticky piston and material out, and then those will activate after.



And do the same on the other side.


Now, you need to begin the redwiring and both sides need to look like this:


After that, you should wire the top. Note the little square. That's used to power the inner sticky pistons.



Okay, I messed up. I missed a row on the back, and I also added some repeaters. Notice that a piece of redstone is missing. And the first and third repeaters are one the third tick.



The other side just has the redstone wires connected. Now, to make the levers that will open the gate. You need to dig three blocks down and make it very spacious; I recommend at least a 4-block diameter. I messed up again and I realized that working on top of sand is a bad idea. I replaced the sand with wood and the size of this hole should extend from one end of the frame to the other side.



Now, to create the XOR-Gate that will allow levers to operate it. The XOR Gate allows a lever on the inside AND outside to operate the gate. You should begin with this design:



Now, you need to connect the redstone wires.



And now, you need to wire out the output, which will go back up. Make sure that the hole is the same depth as the rest.



Back underground, make sure you have a redstone torch ready to send off the signal. You must be sure that the wire connect to the block and not the torch.



So, I messed up again, but it's not that big of a deal. Try to spot where I messed up!



Now, you need to add levers. The levers need to branch off from the sides. You do something similar to the output from the other end, but this time, you don't use a redstone torch. Instead, above the redstone wire is a lever.



Just do the same one the other side and cover everything up! Enjoy!