look at the minecraft wiki, there's all the stuff you need to know. however i thought you need to plant a mushroom in shadow at least under a specific light level.
Mushrooms grow only at light level 12 and below, except when planted on Mycelium, and grow more quickly at light level 5 and lower. This growth rate is determined by the light level of the original - or "seed" - mushroom when growing from a lower light level into a higher light level.  Brown and Red mushrooms grow at the same speed.
I belive you have to plant it below light lvl ..12? maybe 9 im not to sure of that, anyway a roof for some shade or a mushroom-room underground/somewhatdark should help you
As AutoCon suggested, if you get you hands on mycelium you can plant it in daylight
It needs to be in the shade, or in a cave. It can't be planted outside unless you're planting it on mycelium. You can build some shade in the form of a diamond 5 blocks wide and at least 6 blocks high (if you're planning on making large mushrooms), and then plant the mushroom in the center.
Ok, I am officially puzzled. I have a floating isle in the sky (naturally occurring). Underneath that I was able to plant the mushroom. But when I try to plant under clear sky, at night (nightlevel similar low), it does not take root.
And what use is a giant mushroom in the middle of a dense forest?
The common theory has been that mushrooms are having issues due to the prolific lighting bugs right now in the game since the new anvil heights were added. However I'm starting to wonder if at least the shade part was an intentional change by Mojang. It makes sense, since mushrooms do not typically grow well in areas exposed to direct sunlight.
Guy with problem: "I'm having trouble planting mushrooms. I hold the mushroom in my hand, and right-click a dirt square, but nothing happens."
Internet douchebag: "It's easy what are you dumb step 1 put mushroom in dirt step 2 hit mushroom with bonemeal herp derp"
God I love the Internet. The problem, as some of you may or may not be aware, is that we cannot put the mushroom in the dirt! I'm not sure whether it's a bug or a feature, but apparently mushrooms can no longer be planted on the surface, regardless of light level. Only "underground" (i.e. with a solid block/blocks above them.)
i am playing minecraft 1.2.5 in single player mode.
I do not seem to be capable to planting a red mushroom.
I tried in the night, I tried on dirt, I tried on grass, it does not seem to take root.
To plant i hold the mushroom and right click the spot I would like it to go.
What do I do wrong or what needs to be considered?
(Did not find anything helpful using the search)
try building a roof and walls around it that are big enough to fit a giant mushroom, the Minecraft Wiki has information about those requirements. And then, when it's grown (with bonemeal of course) remove the walls and the roof and you have your mushroom. That should work fine At least it works fine for me.
What ive noticed if your trying to plant one somewhere in the night, i think the game takes into account of what the light levels will be like in that area during the daytime, and either let you plant the mushroom or not accordingly, because you can plant them underground all day long(my mushroom farm is at y:12 in my slime farm