Ambition is a two edged sword -- express it and let people know that you've set your career sights higher, that you believe you have more to offer, and that you will be a force to be reckoned with. But it also makes you a threat to some, throwing you into the middle of the Street Fighter and Maneuverer's worlds.
Of course, you could express no ambition -- in which case you will likely be judged as dull, complacent or satisfied with your current lot in life. And if you are good -- really, really good -- someone will probably eventually be asking you why you aren't aiming higher, anyway.
For a ladder climber, expressing ambition is critical to long term success. So what's the best way to do it? This might be an area where first discussing what you SHOULDN'T do gives more in sight.
First, don't be stupidly impatient. I had a manager approach me once just a few days after I joined one of my employers -- he wanted to know what he needed to do to "get ahead" at the company. The discussion felt so odd and forced, I couldn't help but think he was strange. Be keenly aware there is a time and place to express your ambitions to others -- the best time being after a rousing success.
Second, don't run down someone in your target position, and then follow up with commentary about how much better you'd be doing it. Even if the audience agrees with the criticism (the pointing out of which won't earn you any points), they will likely find your brazen undermining attempt distasteful. A possible exception to this advice would be with extremely skilled street fighters -- but pulling it off requires finesse, and I can't recommend such an approach for the vast majority of power players.
Third, don't be too specific, or short term. Don't say you want "Fred's job" -- there's no more certain way to align Fred against you when he finds out. A much better approach is to take aim at a position two or three levels above you. "I'd love to be a plant manager some day" is a much safer approach, and it communicates the ambition just as directly. There is a time to ask for Fred's job -- when it becomes known he's leaving it. Then you shouldn't hesitate to make your wishes know.
Fourth, keep quiet if your recent performance level hasn't quite been up to snuff. A highly ambitious and demanding employee, who is also underperforming, is likely to earn a quick ticket out of the game entirely.
Fifth, DO make visible efforts to improve yourself. That night MBA isn't the only way to do it -- reading and demonstrating new skills and proficiencies, and attending seminars or conferences can also help. As a rule of thumb, I'd recommend making at least one visible effort to improve your skills each year.
But before you say anything to anybody, recognize what you're signing up for when you express ambition --
You may not know when and where the next opportunity may come. It may require a physical move. It may happen when your kid is in her senior year of high school. So don't start the clock ticking if you're going to have to refuse an opportunity. Refusals can typically only be made once in a great while, before the offering manager will decide you really AREN'T a serious candidate for growth.
Can you be a great politician without expressing ambition? You bet. But by indicating your desire to climb the ladder, you put yourself into the stream of political power players.
Do so wisely.