Start your speech by mentioning what an incredible experience you had acting in your Oscar-winning role. Talk about the complexity of the character and what an honor it was to be chosen for the part. Briefly discuss the factors that led you to take the role.
Thank the director, producers, cast and crew of the movie. Mention some nice things about working with these people, particularly the director. With some people, it might be a stretch to find something nice to say, but if you can't think of anything, just mention that person in your general thank-yous.
Express your appreciation to the Academy members for choosing you for this great honor.
Acknowledge your competitors and mention that you are honored to be part of such a talented group. You might want to talk about actors or actresses who inspired you, as Halle Berry did when she won an Oscar for "Monsters Ball" in 2002. "This moment is so much bigger than me," she said. "This moment is for Dorothy Dandridge, Lena Horne, Diahann Carroll. It's for the women that stand beside me, Jada Pinkett, Angela Bassett, Vivica Fox. And it's for every nameless, faceless woman of color that now has a chance because this door tonight has been opened."
Thank your spouse, significant other, parents, children and other family members for supporting you. Mention the sacrifices that family members had to make while you were spending long hours filming.
Use humor when discussing the role or your career. When Robin Williams won the Best Supporting Actor Oscar for "Good Will Hunting" in 1998, he said, "Most of all, I want to thank my father up there, the man who when I said I wanted to be an actor, he said, 'Wonderful, just have a back-up profession, like welding.' "
Finish your speech by mentioning how much winning the Oscar means to you and how you'll always treasure the moment. If you already have a special spot chosen to display the award, mention this in your speech.