Minecraft Nether Fortress Finder
Because one of the needed components is Blaze Powder, which can only be found in Nether Fortresses, finding Nether Fortresses in Minecraft will be vital if you ever want to create an Alchemy Table to produce potions.
To travel to the End, you'll also need Blaze Powder to construct Ender's Eyes. Only Nether Fortresses have Wither Skeletons, which you'll have to battle if you ever wish to kill the Wither. Here is How to Find Nether Fortress.

Information about the Nether Fortress in general
The first thing you should know is that Nether Fortresses spawn in straight lines on the Z axis (North/South).
When I say that they spawn in lines on the North/South axis, I mean that once you've found your first Nether Fortress, you may go north or south to locate others. This is also useful for discovering them at first, because you know they aren't completely random and are scattered rather equally across the Nether.
Obviously, they aren't set out in an exact straight line on the North/South line, and their centers stray a little from this line, but because they are so huge, it's a good general explanation for how they spawn.
Another point worth highlighting is that they can be as near as 150 blocks from center to center in certain cases, and as distant as 600 to 700 blocks in others. Some spawn so near to one other that they effectively combine into a single enormous fortress, though this should be uncommon.
You'll also notice that their depth varies a lot, although I usually go for anything between 60 and 70 on the Y axis. The higher constructions in a Nether Fortress may also reach 30 to 50 blocks in height, so you're certain to come across at least a portion of one and then dig about until you uncover the main building.
Nether Brick is used to construct the primary construction of Nether Fortresses; hence this is the brick you'll be seeking for when excavating. Nether Brick and Netherrack are virtually identical in color, making them difficult to distinguish at first. However, Nether Brick breaks much slower than Netherrack, making it easier to locate the fortresses buried underneath Netherrack.

The Difficulty of Locating Nether Fortresses
For those Survival purists out there who want to do it the right way, I'll teach you how to discover Nether Fortresses the hard way first.
Important: Make a note of the coordinates of your Nether Portal so that you can find your way back!
You'll be digging in straight lines on the Z axis (North/South line) for many hundred blocks in each direction to discover your first Nether Fortress. If you don't locate anything, try moving east or west.
This process might be time-consuming and tiresome, but you will eventually come across one. This is basically the only way you'll be able to utilize if you're playing on a version other than the PC version.
Finding Nether Fortresses Has Been Made A Little Easier
If you want to get a head start on discovering your first Nether Fortress, and you're looking for the one nearest to your Nether Portal, there's an app called Amidst that can help you out (without cheating too much).
When you run Amidst, give it your world seed or point it to your save file, and it will build a beautiful map of your Minecraft world.
Spoiler Alert: If you're a purist, load up a random seed first, then go to the Map menu at the top, pick Layers, and then click on any layers you don't want to view. By default, it shows the position of Villages, Temples, and Strongholds; if you don't want to know where they are, turn off any of these layers.
The Nether Fortress layer isn't enabled by default, so choose Layers – Nether Fortress Icons from the Map menu.
It's vital to remember that coordinates in the Nether differ significantly from those in the overworld. It's not possible to travel to one of these locations in the Overworld where a Nether Fortress is shown and then make a Nether Portal to discover one nearby; it just won't work. You'll have to ignore the locations because it basically only indicates where they are relative to each other inside the Nether.
Instead, use the places Amidst provides as a broad suggestion to where you might be able to find one.
For instance, in the seed I described above, I created a town around the NPC village in the map's middle. If I want to discover the nearest Nether Fortress to my village, I'll probably have to make a Nether Portal there and go northeast a couple hundred blocks.
While this approach is far from scientific, it might point you in the right direction and save you a lot of time.
Easily Locate Nether Fortresses
So you've tried both of these ways and come up empty-handed. What now? Well, I've got a lot quicker way to discover your first Nether Fortress, and it'll work even if you're on a Survival server that's been closed down.
You'll utilize a combination of the two ways above, as well as an X-Ray texture pack, to locate Nether Brick among the mountains of Netherrack.
I'll admit that this is a bit of a shortcut, and I'd only do it as a last option, but I can almost promise you'll locate a Nether Fortress this way.
Strongestcraft is my fave texture pack for this. The one entitled “Strongestcraft F&MF,” which stands for Fotress & Mycelium Finder, is the one I use the most. This texture pack turns Nether Brick into a brilliant green and renders Netherrack almost invisible, making Nether Fortresses stand out like a sore thumb.
I will warn you that utilizing this texture pack to travel through the Nether should be done with caution, since it can be difficult to see cliffs and drop offs if you move too rapidly. I can't tell you how many times this has caused me to fall big lengths, so you might want to start by turning it on after a few blocks and then turning it off if you don't see any fotresses nearby.
Remember that your viewing distance is still vital while doing this, so set it as high as you can without crashing your computer.
Finally, if you're having trouble discovering a Nether Fortress, change the game mode to Creative and fly about. This is about as simple as it gets, but if you want to return, you'll need to locate a path to dig a pathway there.
Are you still having issues? Leave a remark and I'll do my best to assist you.