First, create the script. Open a sudo version of our editor, such as leafpad, with the command gksudo leafpad.
Then, your file will look something like this:
#!/bin/sh
amixer set Master 64+
amixer set Master toggle
Save this file somewhere it will -never- be moved, I reccomend /usr/loca/share, call it something like boot.sh
then type sudo chmod +x /usr/local/share/boot.sh
then, create a new file, and save it in the /home//.config/autostart folder. If autostart does not exist, create it. The . infront of .config means the file is hidden, make sure you are viewing such.
Now, name this file boot.desktop (or whatever, the .desktop part only matters), and make it something like:
[Desktop Entry]
Version=1.0
Encoding=UTF-8
Name=Audiofix
Type=Application
Exec=/usr/local/share/boot.sh
Icon=
Terminal=false
StartupNotify=false
Hidden=false
GenericName=
GenericName[en_US]=
Save, reboot.
Mission Accomplished, assuming you use XFCE.