Whenever I do potatoes that are chunked or cubed, I always precook by steaming them, whether on the stove or the microwave, to where they are just barely beginning to soften on the outside. Then I dump them on paper towels to blot off excess moisture, then continue cooking from there. They always come out nicely browned/crispy/crunchy on the outside and soft and fluffy on the inside.
If I cook sliced potatoes, I start them out covered, then uncover for last 10-15 minutes so they'll crisp up nicely.