I suppose there are some general principles that could be laid out, but I also imagine that applying them will look different depending on the age of the student and the objective.
An example from my own teaching:
I have my senior rhetoric students memorize and perform several speeches from Shakespeare. My goal is three-fold: 1) to have etched in their mind well-crafted words, 2) to better understand human nature, which Shakespeare displays so well, and 3) to have better command of their own rhetorical delivery.
First, I perform the speech for the students, to show them a model of what they will themselves look like when they've completed the task. From this point forward, we'll practice the speech in class daily as a simple repetitive exercise until the students have the speech memorized. I have a variety of exercises beyond bare repetition to help the students enjoy the activity in different capacities (for example, I'll have one student be an actor and another be a director who must order changes of emotion--angry, sad, happy, contemplative, etc.--just to get the students thinking about what such emotions would look and sound like with the words).
Second, we watch other examples of actor portrayals and discuss the different choices that the actors have made. This allows the students to see that the character isn't limited to one way of portrayal, but it also sets up opportunity for debate once we've read the play and have to draw some hard conclusions about the character that will close off some interpretations actors have made. I also use John Barton's Playing Shakespeare video series to help students understand some of the principles that go into performing a character in Shakespeare.
Third, we read aloud the play together, pausing to make sure everyone understands the action, and to discuss the character whose speech we are memorizing at various points in the play. At this point the students know the speech pretty well, but having it in context often brings out things they hadn't considered before, and maybe even impact how they've imagined the pace or emotion of the speech that they've been assuming (or adopting from one of the examples). By this time the students have pretty well memorized the speech and made their own choices about performing the character.
Fourth, we watch a version the play together to put the whole package together and as a kind of celebration of their work.
Even my weakest speaking students perform beyond their average ability, and they all come to some clearer understanding and appreciation of Shakespeare's characters (and I hope, though it is harder to tell, of human characters), though they don't always agree with me :-).