The audience is sitting in their seats, eager to hear your speech or presentation. If the first words you utter are the entirely predictable and boring "Thank you for giving me the opportunity to speak with you today" you've dug yourself a hole about 2 feet deep. If you continue with the tired old "Today I am going to talk to you about point one, point two and point three" your hole is now about 5 feet deep. Pretty hard to climb out of!
What are the alternatives? Try one of these three:
1) Use an evocative action word or phrase such as "Imagine..." or "You should have been there." Follow your choice with something dramatic or funny or incongruous. The point is that these unexpected openings are immediately attractive and you are at least starting from ground level if not above.
2) Put the word "you" in the first sentence, such as "Every day you come to work with your eyes on your mission." (Then state the mission in one sentence.) Or begin like this: "What would you do if...?" (state a challenge or problem or dilemma).
3) Tell a story. Your story must be relevant to the call-to-action of your speech or presentation and it should have meaning to the audience. Just because you love to play tennis, doesn't mean you tell a tennis story unless you can tie it to the needs of your audience. If you select your story based on the goal of making your story their story, you'll get their attention right away.
No audience member was ever disappointed by a speaker who was interesting. Do not fall into the trap of being boring. Grab your audience with a compelling opening and you'll have the best chance of making a positive lasting impression.