The objective is to make a spherical-typed (360 degrees) panoramic photo,
With 2:1 aspect ratio, and its dimensions are 1024x512 or 2048x1024.

Tried searching in Google but still don't know where to start.
Please describe a step by step guide.

Possible questions :
What are the needed tools for taking the photos ?
How many photos needed to be taken ?
What is the best software for stitching those photos ?
And how to use it ?  

If there are anything I missed, please mention it.
Thank you very much !

Update :
I want to make an Android application that displays virtual tours with spherical panoramas.
In one scene, there is something like a ball / sphere, with the camera inside, on its center, and the user can look freely in 3-dimensional 360 degrees.

I'm using PanoramaGL for Android (https://code.google.com/p/panoramagl-android/), by Javier Baez.
The sample panoramic photo looks like this : (Photos by Geovanny Raura)
http://imgur.com/4VW66IV,rZm8pB5,4hhwJEc (There are 3 images)


Question: Shalom alecha rebbi (u'mori)
Answer: I once heard from my rabbi in high school that it was about 3 seconds. Not sure the source,  but it always made sense to me. Witnesses also must recite their identical testimony within that same timeframe.