You want to go certain run level in Fedora or Red Hat Linux with GRUB.
on boot at GRUB splash screen
press any key
select boot option that you want boot from
press a to append
press space and write here which run level you want to go (1,2,3,emergency,s)
kernel /vmlinuz-2.6.9-5.ELsmp ro root=LABEL=/ hda=ide-scsi rhgb quiet 1
press enter and booting...
BTW brief information
1 : this is going to process rc.sysinit and rc1.d scripts
s, S, or single : this is going to process only rc.sysinit
emergency : this is going to run sulogin only