Prepare a large baking sheet by lining it with parchment or wax paper.
Prepare your fruit by cleaning and thoroughly drying it.
Coarsely chop the chocolate, reserve 1/4 of it and finely chop that portion. Transfer the coarsely chopped portion to a microwave-safe bowl.
Heat the chocolate on full power for 30 seconds and stir. Heat another 30 seconds and stir again, scraping the sides and bottom of the bowl with a rubber spatula.*
Continue heating the chocolate in bursts of 5-10 seconds, stirring vigorously after each one, until the chocolate is 70% melted. At this point the residual heat should melt the chocolate as you stir.
Once the chocolate is fully melted and smooth, add half the FINELY chopped chocolate and stir until fully melted.
Add half of the remaining finely chopped chocolate, and stir again until fully melted. Keep adding chocolate, 1 or 2 tablespoons at a time and stirring until melted.
When it starts to take a few minutes of stirring before the added chocolate fully melts, test the temper by dipping the back of a metal spoon into the chocolate and setting it down on the counter. It should start to set after about 5-8 minutes. Keep stirring while you wait. If it has not set, add a little more chocolate, stir until melted and try again. Your chocolate is tempered when it sets with a beautiful shine and no streaks.
One by one, dip each piece of fruit into the tempered chocolate, and give it a little shake to remove excess chocolate. You can also give it a little scrape on the rim of the bowl. Set the fruit down on the prepared baking sheet (or dip it in something else if you like - see post for suggestions).
At this point, you can sprinkle the dipped fruit with nuts or sprinkles before it sets, or wait for it to set and drizzle it with white or milk chocolate if you like.
Serve immediately, or store UNCOVERED on the baking sheet in the refrigerator for up to 2 days (optimal storage times will depend on the fruits used). Very dry fruits like strawberries and cherries can be left at room temperature up to 24 hours.