Whether you're creating a whole new system of government, or just trying to change a few local policies, there are a few things that one should always keep in mind:
Do your research! Get all the facts straight before writing up your proposal, and find out if there are any solutions already in the works.
Be specific! If you can't write up a detailed solution to a problem, including financing, then get help from someone who can.
Consider the worst-case scenario! Think of every possible way that your plan could go wrong, how an unscrupulous person could take advantage of the new system, or what sort of unintended consequences might arise. Then adjust your plan to prevent as many of these as possible. It will never be 100% foolproof, but you can minimize the risks.
Don't include impractical add-ons! Remember, you're not worldbuilding a novel. You're trying to solve a real world problem in the most practical way possible. Don't tack on a bunch of unnecessary details just because you think they're cool.
Be willing to give up your idea for a better one! Regardless of how much work you put into your solution to a problem, or how proud you are of it, your first priority should always be to fix the problem in the best way possible, even if that means throwing out your own idea for someone else's.
Know where to compromise and where not to! Any plan is going to have some aspects to it which can be changed or substituted without deviating from the original intent, and some which are vital to the original intent. Don't confuse the two.
Don't seek personal wealth or power! People will be less inclined to go along with your plan if they think you're doing it for personal gain. Don't even begin to plan on how to capitalize on your victory until after you've succeeded.
Be willing to give up credit! I'm not saying you should avoid taking credit, but if it comes down to a choice between solving the problem and taking the spotlight, solving the problem always comes first.
Be honest and direct! You're going to need public support, and you're far less likely to get that support if people sense that you're being deceptive or manipulative.
Avoid being adversarial! If someone disagrees with your plan, do not make an enemy of them. Be polite and considerate. If your plan is going to succeed, you're going to need support from as many people as possible, and you won't get that if you keep making enemies.
You can't please everyone! There will always be a few people who, no matter what you say or do, will never accept your proposal. Give them your best shot, but if it's not enough, just move on. Otherwise, you'll end up wasting valuable time.
Don't respond to personal attacks! When you propose a new idea, there will almost certainly be someone who wants to debate you on the subject. Address all their concerns, but if someone ever tries to steer the conversation away from criticism of the proposal and into ad hominem territory, your best response is to steer the conversation back to the proposal. Remember, you're promoting an idea, not yourself.
Don't get caught up in promotion! Raising awareness for your proposal is an important step in the process, but if you're spending more time hosting events and giving speeches than you are in meetings with influential figures, then your whole project is certain to get stalled.
