Well, I'll throw out a few points about what it means to me. This is not a comprehensive picture and I am concentrating on the points which would distinguish me as a Leninist from a self-described 'radical', 'democratic socialist', 'non-Leninist Marxist', etc.
(a) First, it means to be really serious about getting a socialist society. Not just some reforms here and there, not just affirmative action, a safety net, and so on. We need a radically transformed human world. We are really intent on getting one. We are intent on studying the question of how it can be gotten very hard. We intend to be, to capitalism, what physicians are to disease.
(b) Next, it means believing that the series of revolutions beginning with that of 1917 were generally a positive development and have lessons to teach us, and in some way show us the direction we have to go and the things we have to do, or redo; they were not just some horrible dead end that humanity went into.
(c) It means always remembering that we are here as representatives of the workers and oppressed, and for that matter the workers and oppressed of the entire world, not of whatever stratum we happen to be in at a given time, and not of our own desire to make the world a nice place. If we are putting forward a position that can't be explained to the poorest and most exploited, it's probably the wrong position.
(d) It means having a practical and dialectical approach to the struggle; that is, that one is trying to put forward the demands and shape the intermediate steps of the struggle in such a way that more people are radicalized and involved, and connections are made, and the struggle is moved forward. As opposed to worrying about writing 'the best possible piece of legislation' about something. And it means dealing with one's own tasks in one's own country and situation, as opposed to drafting a master plan for the world. (I know there are "Leninists" who act differently, but there is very little in Lenin's practice to support them.)
(e) It means maintaining independence from one's own imperialist ruling class at all times, never being overcome by the desire to be 'respectable' in their eyes, and refusing to be associated with its wars, war propaganda, schemes for global influence, and so on.
(f) It means acting toward people of oppressed nationalities, and of other oppressed groups, with sensitivity and with respect for the principle of self- determination. I find Lenin's writings on the national question to be the things I go back to most often.
(g) On the organizational side, it means a belief in the proposition that people who are agreed on what they want to do, and generally on the science and engineering of how to do it, and discuss the matter openly and honestly among themselves, can get a great deal accomplished (including what they get done by persuading other people of the correctness of their ideas), and that it is a good thing to have a party that is organized on that kind of basis.
That's what comes to mind at the moment.
LP