The Mojang team have released a "pre-release" version of Minecraft 1.9
First and foremost; this is a pre-release candidate. Bugs and lag-related issues are to be expected. Secondly; remember that absolutely no mods will work with this pre-release, and will not work until Bukkit release a new Recommended build.
Updating your Minecraft Client:
- Close out of minecraft, you'll have all the files you'll need.
- Download and save the file.
- Go to C:\Users\AppData\Roaming.minecraft\bin Or just type %appdata%/.minecraft/bin - Inside that folder will be minecraft.jar,
- Replace it with the one you just download.
- After you replace it, run minecraft.exe again and this time play the 1.9 pre-release.
Download:
Minecraft Server 1.9 pre-release
Minecraft Client 1.9 pre-release