Macbook pro will only show blank screen on start up. Starting it up via cmd T will show terminal sign, but connecting it to iMac by firewire will not show Macbook in finder on iMac. How can I try to start up Macbook?

Try the steps i9s the Apple document Resolve startup issues and perform disk maintenance with Disk Utility and fsck (http://support.apple.com/kb/TS1417). If non of these steps help take it to a repair shop because something hardware really broke. It could be a bad hard drive or worse.