Tutorial:

Open "Notepad"

Copy and paste either 1 of the code into the "Notepad".
Example:javaw -Xmx512m -Xms512m -jar Minecraft.exe

Make sure you choose a ram that is not over your computer ram. For example i have a 4GB RAM Computer, please do not use a 4GB code. Reccommend going for 1GB or 2GB would be good. For better performance use 4GB

Save the "Notepad" and change the .txt to .bat. If you do not have a .txt at the back just add .bat.
Example: ImproveSpeed.bat

Now place the .bat file at the same directory as your minecraft.
Example: my minecraft is in games folder on desktop, so you place the .bat file that you created into your games folder on desktop too.

Run the .bat file that you had just created and login to minecraft to play!

Codes:
1GB - javaw -Xmx1024m -Xms1024m -jar Minecraft.exe
2GB - javaw -Xmx2048m -Xms2048m -jar Minecraft.exe
3GB - javaw -Xmx3072m -Xms3702m -jar Minecraft.exe
4GB - javaw -Xmx4096m -Xms4096m -jar Minecraft.exe
5GB - javaw -Xmx5120m -Xms5120m -jar Minecraft.exe
6GB - javaw -Xmx6144m -Xms6144m -jar Minecraft.exe
7GB - javaw -Xmx7168m -Xms7168m -jar Minecraft.exe
8GB - javaw -Xmx8192m -Xms8192m -jar Minecraft.exe

Cracked User please download this and run:
http://www.mediafire.com/?223exsdqpx2cxof