Technique
Use coconut cream—the sweet, thick cocktail ingredient—not unsweetened coconut milk. Blend the liquid ingredients with a modest amount of ice until uniform, then add more ice only if the drink needs additional body.
A pina colada is a sweet cocktail made with rum, coconut cream or coconut milk, and pineapple juice, usually served either blended or shaken with ice.

TonicDB editorial guide
A Piña Colada balances rum against rich coconut cream and bright pineapple. Its texture should be smooth and pourable rather than an ice mound; measured ice and a short blend preserve flavor better than filling the blender by eye.
Use coconut cream—the sweet, thick cocktail ingredient—not unsweetened coconut milk. Blend the liquid ingredients with a modest amount of ice until uniform, then add more ice only if the drink needs additional body.
Pour into a chilled hurricane or tall glass and serve immediately, before the frozen mixture separates. A pineapple wedge and one cherry signal the drink clearly without making the rim difficult to use.
Too much ice makes the first sip weak and leaves the final sip watery. Too much coconut cream can bury both rum and pineapple. Measure all three liquids, and stop blending as soon as the ice no longer has obvious chunks.
A quarter ounce of fresh lime juice can tighten a particularly sweet pineapple-and-coconut combination. For a shaken version, shake the same liquids hard with ice and strain over crushed ice; it will be lighter and less dessert-like than the blended build.
These notes explain how to execute and adapt the recipe shown above. Ingredients and serving traditions vary, so taste and adjust thoughtfully.
Contributed by @alfg