Know the facts - but don't rely solely on them. Make sure you frame your idea within a strong narrative. People make decisions based on their emotions and intuition, as well as on rational thinking.
Talk to the right people. Find out who the main decision-makers are, ask for their feedback, and make sure you listen to their response. By doing so, you'll be able to show them later how you've incorporated their thoughts.
Make it relevant. Link your ideas to the priorities of those you're trying to sell them to. This allows potential customers to see what's in it for them. Decision-makers will inevitably see your idea from their perspective, so understand what motivates and drives them, and tailor your pitch accordingly.
Find safety in numbers. The more widely supported your proposal seems to be, the harder it will be to reject.
Break it down. Slice your argument into bite-sized pieces. This allows people to review the information at their own pace. If you rush them, they may become overwhelmed and reject the idea out of sheer confusion.
Do your homework. Be ready for awkward questions. Even the boldest decision-makers need to cover their back, so don't downplay potential objections; anticipate them, and be ready with a convincing response.
Present with conviction. Make sure it's clear that you believe in what you are selling. If you're not confident, don't expect others to be.