Try cleaning the disc(s). Fingerprints and smudges will prevent the optical drive from the read the disc.
Hold the Moyse button down to eject Disc #2 while booting up, at the same time hold the Option/alt key down to have the startup manager pop up, insertt Disc #1 & wait For Disc #1 to show as a boot choice.
That second Disc thing happens frequently, the best way around it is to do a Custom install, and eliminate enough Printer Drivers, Languages, Fonts, and Applications you don't need... then it may skip #2 altogether.
2. When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu. (In Mac OS X 10.4 or later, you must select your language first.)
Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.
3. Click the First Aid tab.
4. Select your Mac OS X volume.
5. Click Repair. Disk Utility checks and repairs the disk."