Know your lines inside and out, backwards and forwards. Repeat them until you are saying them in your sleep.
Meditate on your character. Review the personality, history and intention of the character. Form an understanding of the character you are portraying. Decide what would be his or her truth and intention in presenting this speech.
Map out a general pattern of movement corresponding with the script. Decide whether the you should sit, stand or walk about. Think about what would be natural to the character and his or her mood.
Speak your piece aloud, incorporating the prearranged movements until they come naturally together and without hesitation.
Allow yourself to put on the character. Get a feel for the facial expressions and gestures that will express your intent fully, but without seeming false.
Practice the entire package on the stage so as to get a feel for the geographical area and atmosphere in which you will be performing. Assimilate whatever props you will need.
Repeat the process until it is your second nature, like a comfortable cloak to slip on before you walk onstage. The inspiration will flow from practice and, of course, the addictive presence of an audience.