There is NO standardization between EFI-based computers regarding accessing boot-time options. It can usually be done in much the same way as with BIOS-based computers -- by hitting Esc, Del, or a function key early in the boot process. Some EFIs have removed this option, though, which can lead to the sort of problem you're seeing. Using an external medium with a third-party boot loader may provide a way out in some cases. Try the CD-R or USB flash drive of my rEFInd boot manager for this. Posting the make and model of your computer, or asking about it on a manufacturer's forum, may also provide answers.
If you can physically remove or unplug the hard disk, you should be able to force the system into the firmware setup utility, which may enable you to adjust firmware boot options. When you reconnect the disk, you might then be able to get a boot menu to select a recovery tool.