Boot process consists of a sequence of stages which you can save as an image file and view it after your system is booted using a tool called bootchart.Install bootchart by using the following command in the terminal.
$sudo apt-get install bootchart
Next time you will boot , the result will be stored in /var/log/bootchart directory as a .png file.
Now verify the bootchart to see which processes are started automatically.There are some processes that can be stopped without any performance degradation by going System-->Preferences-->Startup Applications.
Some of them are
i)acipd: It monitors battery level of laptops and special keys of keyboard like Volume Control,Web browser
access etc. If you don't use a laptop and don't have a keyboard with special key functions you can
turn this off.
ii)apmd: If you don't use laptop you can disable it. (Even if yoy have a new laptop you can disable it)
iii)dns-clean , pppd-dns , ppp : If don't use dial up connection you can disable them.
iv)pcmcia , pcmciautils : If you don't have any PCMCIA slot in your machine then turn this off.
v)rsync: Used to syncronize files among computers. Disable it if don't need it.
vi)powernowd: Only useful for new pcs that cpu frequency scaling. disable it if your PC doesnot support
scaling.
vi)bluez-utiles: Turn it off you don't have any blue tooth device.
viii)fetchmail: A mail receiving deamon. Can be turned off.
ix)readhead: It preloads libraries which make some application start faster but make boot process slower.
x)cron: A job scheduler . Can be turned off.
Another Tip: If you see ureadahead( a process that pulls files into memory ) is taking too much time then use
the following command-
$sudo rm /var/lib/ureadahead/*pack
