Pina Coladas aren't the sort of thing I make very often, but from time to time, they're the kind of "change-up" drink you like to have in the repertoire. Great at parties, too. They're kind of unwieldy to explain in writing, though. A smooth, drinkable consistency is what you want; no big chunks, but not soupy either. It'll be obvious. For two drinks, start with two modest handfuls (one cup?) of pineappe, blend it up, and see what you're left with. Too thin? Add more pineapple and/or ice. Err on the side of too little pineapple to start, though: it's easy to add more and you want to avoid adding more and more liquor (or ice or water) just to thin out the drink. Be sure to remove the rinds of the pineapple before blending, and save the leaves for garnish.

For two:
two moderate handfuls of cubed, peeled pineapple
two shots light rum (cheap!)
one shot coconut rum (Malibu, etc.)
four or five ice cubes.

Place all ingredients in a blender. Blend with the lid on for a few seconds as a vortex forms in the center. Test for consistency: it should be potable but viscous, though not like a chunky slurpy or oatmeal. If you want a thinner drink, add more rum or, to keep the octane down, water or ice (but go light). As a rule of thumb, it's better to add pineapple than rum, so start with a small amount of pineapple. If the drink is still too thin, just add more.

Pour into a snifter with tacky etching and garnish with one of the pineapple leaves.