According to my research, the elements of successfully infusing vodka are ingredients, proportion, time, and tasting.
Wash and slice the flavor elements into largeish fruit-salad-sized pieces, but leave berries whole after removing stems and leaves.
If infusing non-berry fruit, use 1-3 largeish fruit-salad-sized pieces for 750ml of vodka. If using herbs, use 1-2 fistfuls of the herb (depending upon the potency of the herb); with berries, use 2-4 fistfuls. You may want to berries or herbs a little before adding the vodka, although if you squish them too enthusiastically this will make the vodka cloudy. In general, the more of a given flavor element you use, the less time it will need to infuse (see section IV).
Generally, citrus fruits or strongly-flavored ingredients infuse in less than a week, but mellow-flavored or fibrous flavor elements (like watermelon or fresh ginger) can take a week. Really light flavors like cucumber and lavender can take as long as two weeks.
If you can’t tell if it’s done, taste it! If the flavor is too weak, leave it be for another couple of days; if it’s too strong, dilute it with more vodka and allow it to infuse a little longer
Fruits will continue to ripen while infusing, so remove fruits before they get over-ripe as it will impact the flavor of your recipe (e.g., sliced pears or apples will continue to brown).
If you use a small or particulate flavor element, you may want to strain it out of the final product: line a wire mesh strainer with cheese cloth or coffee filters, set it on top of a bowl or pitcher, and then pour the stuff through.
Our final list was. . .
The Js: Ginger, espresso (grounds or beans?), pomegranate, and mushroom
K & L: Lime, vanilla, raspberry, green apple