Step 1: Pick your Pears
Step one: find a fruiting cactus. Bring tongs.
This can be significantly easier than you might think. When I was a teenager living in Colorado, my friends and I would come across wild prickly pear cacti, bearing tiny fruits about the size of a super ball. Like many wild fruits (ever tried wild strawberries? They will BLOW YOUR MIND) the flavor is concentrated and intense, but it's completely impractical to collect enough to make anything with them.
Nowadays, I live in the muggy southeast instead of the arid southwest, and prickly pear cacti are weirdly easy to find. Around here (and, apparently, in much of the US), prickly pear cacti are a common landscaping plant. As summer wanes into fall, these enormous cacti (sometimes standing 5-6 feet tall) will become covered in yellow flowers, which will turn into plum-sized fruits.
To pick the fruits, grip them with the tongs, and gently twist the fruits off the cactus.
Why tongs, you ask? Well, do you see those little fuzzy spots on the fruit? The ones that look like they might be soft as a newborn baby's hair? Those are called glochids, and they are really bundles of hundreds of tiny fiberglass-like spines. While you're busy worrying about the long, scary spines on the pads of the cactus (known as "nopales," they are also edible!), the little hairy spines will detach and embed themselves into your skin. It's likely that you won't notice that this has happened until you brush the protruding end of one of these evil little spines into something, and it feels like you are having a tiny hole drilled into your skin. By a laser. A laser that is ON FIRE.
These spines can be dislodged from the fruit really easily - be very sure that you stand with your back to the wind while you pick these, as I cannot even imagine how horrible it would be to end up with a glochid in the eye.
If the fruit "gives" a little, and twists off easily, it's probably ripe. I'll be honest here: I have no idea when prickly pear fruit season is. I've read it's supposed to be in the late fall, but I collected these fruits in late November (they were delicious). So, late fall to early winter?
Put your fruits into a paper bag or other impenetrable container. Plastic bags will not stop the glochids from sticking you.