The hood release cable on my 1990 Lumina has broke. How do I open the hood from outside the car?

Ho Pob! You have three ways to go about this. First I'd trace the cable and try to find a place beyond the break in the line inside the drivers compartment. You are going to have to replace it anyway so you basically cut the cable and pull back some of the covering. At that point you can grab it with a pair of vice grips and try to activate the latch. if that's not possible or the break is in the engine compartment you can try to activate the hood latch manually by either removing the front grille (if that gives you access to the latch, in some cases it won't) or coming up from underneath the car. Now if you value your time and sanity you may just want to dump the job on your neighborhood mechanic who will replace the cable. Let him deal with opening the hood! Good luck!