1. Your level of preparation, and
2. You ability to act based on "what is happening".
How is that possible? Actually, both are linked and the second one is not possible without the first one. At each moment of time, you need to have your "elevator pitch" ready: thought through, rehearsed, up to date. Ideally, you have several "elevator pitches" based on the "persona" (or the type of person you are talking to). It could be a C-level executive who does not know you yet, or a head of your department who knows you but does not get to talk to you frequently, or a client, or an important stakeholder in a specific project. Have several version of your elevator pitch ready. This could be:
"Hi, I am Stephen Jenkins. I work in the Credit Compliance group. We just launched a new application for small business. The feedback has been overwhelmingly positive. 150 new subscribers in the first 10 days. Would you like to come to our product demo on Monday?" (this is for your company executive who may not know you)
or a similar version for Jeff, a company client who you've met before: "Hi Jeff. Remember me? Stephen Jenkins from Credit Compliance. How is your experience with us? (Pause to listen to Jeff's remark and respond accordingly. Then, if situation permits, describe the new product functionality, if applicable, and invite Jeff to your demo.)
But most importantly, listen more that you talk. "Elevator pitch" is not for you to talk, it is for you to seize the opportunity and use it to establish relationships. Remember, people like the sound of their voice most.
Once you get to speak, introduce yourself. Start with an informal greeting: weather, family, latest company's town hall, competitor's announcement - anything that is relevant to the person you are speaking with. Continue with the first two points most important to you and be prepared to turn this into a two-way conversation, or give an opportunity to your counterpart to share their thoughts. Make this experience positive and memorable to both of you. Listen and tune in.
And finally, be smart in creating such "elevator pitch" moments. Don't miss on opportunities to do so. Obviously, don't stalk your executives. When forced, these encounters always feel disingenuous and will hurt you rather then help you. However, if you are invited to an executive meeting, reach out to one or two stakeholders to get their buy-in and advice in advance and use this opportunity to introduce yourself, if this is within the company culture. If you come to an executive meeting, come 10-15 minutes early, and you will be amazed by the meaningful conversations that you will get involved in prior to the meeting and the relationships you will start building. Never miss on a chance to meet an executive or to ask a question that you are interested in. And always make sure to come prepared with your "elevator pitch".