Solution for v1.2.5 with the TA Walkthrough
Okay, here's my solution for the complete Minecraft n00b that may also (like me!) just try to get the achievements with the great walkthrough from Itzz Sh0wt1m3. I'm going to refer to the walkthrough quite a lot.
If you play this without the walkthrough let me know and I will try to rewrite the solution a bit.
Text from Walkthrough (Minecraft (Win 10) Walkthrough
... Then, pick up some nether wart from the chest. Press right mouse button while aiming at the brewing stand, and then place the nether wart as an ingredient. Wait for the arrow to turn completely white. After that's done as well, pick up your potions...
This does not work. Placing the nether wart in the brewing stand doesn't do anything.
Here's how I fixed it: Just leave this be until you get to the part of the walkthrough that makes you pick up a lot of items for
You will need the blaze rod in a bit. Now continue the walkthrough until you get the crafting achievements or walk to the crafting tables right away.
This is where you go for the crafting achievements:
Place the spare rod(s) on the crafting table to create Blaze Powder
Now walk back to the brewing stand and place all the items as you see on the picture below. It should initate the crafting process right away. I fetched the screenshot below after it finished, that's why it doesn't show up.
You have now crafted a strange potion. The achievement popped like 1 minute later.