Be sure to get the last word. People have short memories. If you do not get the last word, no one will remember what you have said. If this requires repeating your argument 50 times, so be it. This may appear repetitive, however, which will cause people to begin ignoring your messages; you may wish to alter a few words each time rather than repeating it verbatim. This will make it appear as if it were an entirely new message.
Reply to every comment. Not addressing the concerns raised by others will make it appear as if you are evading them. Thus it is important to address every comment made in a thread. If you are discussing on the mailing list, you must reply to every message. If you consolidate your responses, some people may miss that you have responded to a point addressed in another message. Therefore, you should reply to every message, even if your reply is only one sentence long and contains the same argument you have already made.
Remember that Wikipedia is an experiment in mob rule. The only way to ensure that your position is heard over the din is to create a mob. Sometimes, there are so few reasonable people willing to support you that you must create your own mob. Be sure to give them clever names subtly reinforcing your position, as this will make it appear that these editors have already shown an interest in your position and are merely supporting an issue they are concerned about, rather than being sockpuppets. This will create a majority on your side and you will win.
Be bold in updating policy. This is a wiki. If policy does not conform to the way things ought to be done, edit it. Editing it right before you cite the relevant page will impress others: they are not up on the new policies, and you are.
Assume that you are more intelligent and rational than your opponent. This is usually a safe assumption. After all, if they were as intelligent as you were, they would agree with you! From here you may argue from the position of intellectual and moral superiority. Stating that if other editors would just consider the problem for as long as you have, they would come around to your point of view, is an effective response. After all, how can they argue? They have been wasting their time editing their own subjects, while you have remained the staunch defender of yours for your entire editing career.
If you are alone, you must be right. All great geniuses were at first standing alone with their visions while the rabble persisted in their misguided way of thinking. Therefore, if you are the sole holder of an unpopular position you know will solve the wiki's problems, you are thinking ahead of the crowd. If you are alone, do not back down; opposition only proves how much your input is needed to correct bias. If they tell you that you're all alone, explain that Wikipedia is not a democracy and cite 'Wikipedia:What Wikipedia is not'.
Do not water down your language. Using words like "I think" and "in my opinion" water down the effect of your argument. You must state, unequivocally, that your position is the only reasonable one. If it is true that it would be idiotic to disagree, intellectual honesty requires that you say so. Calling the intelligence of your opponents into question will shock them out of their misguided thinking and make them question their assumptions, and eventually come around to your position.
If all else fails, remember that Jimbo is on your side. Wikipedia was created to be a free, open encyclopedia that anyone can edit. And that means you. By shutting out your positions, other editors are censoring you, and that runs counter to the spirit of the project. Bringing Jimbo into it by leaving a concise message on his talk page (6 or 7 paragraphs will do) will assure that the others will see the error of their ways.
