After using your Mac for a while you will install more and more programs. Many of these programs, as well as your self, will set them selfs up to start up at login. This may be useful if you want an application to start as soon as you log in. But it can cause problems by slowing down you machine. It easily fixed and you should see an immediate improvement in the time it takes to login.
It find you login items open System Preferences > Accounts > The Account In Question > Login Items. You should, if you have found the right dialog box see something like the image below.
As you can see there is a lot of programs and applications that are running at login. All of them consume CPU cycles and RAM. To get ride of them simply select the program you want to remove and press the negative arrow below the list box. That will remove it from the list and it wont be run. You can also right click on any application in the dock and uncheck “Open At Login”. This shortcut wont work for applications that don’t have a dock item. Such as programs that run in the menu bar.