How to get better at debating

Natural talent is, of course, a necessary condition for being an excellent debater.  But frequently the real bottleneck is getting serious about becoming a better debater.  This seems counter-intuitive; many moderately experienced debaters drive themselves to frustration, going to one competition after another without feeling any appreciable improvement.  They seem to exert great effort for little reward.

However, even though these debaters are trying hard at debating, they often aren't trying hard to improve.  Learning the initial steps of debating is easy; how the format works, how to structure a speech, the basics of speaking in public.  These are easy to teach.  Progress in these aspects is frequently swift and smooth.  But once that honeymoon phase is over, you need to take charge of your own development as a debater.  Improvement becomes much more difficult; it requires much more reflection and the ability to be self-critical.  Frequently one can plateau for a period of weeks or months, and any advancement comes in sudden, discontinuous jumps that accompany cracking the next step in an internal puzzle.

I'd like to give some advice to moderately experienced debaters who would like to try to become really good.  I'm not (in this post) going to give general recommendations about how to debate well; those will vary massively from case to case, and can be acquired from a rich variety of good sources.  To be precise, rather than advice, I'd like to give meta-advice; a set of directions for how to take charge of your own improvement.

1. Analyse your performance with your partner after each debate.  What did you do well?  What did you do badly?  What specifically could you have done differently, either individually or as a team, in order to place higher?  What broader strategies for improvement can you abstract from this particular performance?
2. Ask for advice on what you can do better.  It's especially important to ask experienced judges who gave debates against you; they will frequently have a better understanding of your weaknesses than the judges who gave debates for you.  If you disagree with the decision, you should make especial effort to listen carefully to the judges, without hostility or defensiveness.  You need to understand why the decision was made, so that you can win in future.
3. Make a list of what it is you need to do to improve.  There are so many aspects to good debating that it is difficult to improve without knowing what it is that you're trying to do better.  Make a list; add to it after each debate, by reflecting on your performance.  Before each debate, choose one or two items on that list, and focus on doing those things well.  ('speak more slowly', 'illustrate arguments with examples', 'don't use jargon', etc.)  After each debate, ask yourself if you succeeded.  Gradually, more and more of the items will become instinctive, and you won't need a list to remind you to do them.  New items will take their place.
4. Stop blaming the motion.  Or the judge.  Take responsibility for your own wins and losses.  Blaming the judge is frequently a way of disclaiming responsibility for your performance, and hinders the critical self-reflection you need to get really good.  Yes, there are unfair motions and bad judges.  But even if the motion is unfair, or the judge biased, your performance is still causally linked to the outcome.  Almost always, there is something you could have done that would have caused you to win.  Figure out what that is.  Unfair motions and bad judges are, unfortunately, always going to be part of debating.  You need to learn to win consistently, even when fighting uphill, if you want to be excellent.  If you only know how to win in front of an excellent judge, then you will throw away many points that better teams will scoop up.  (Of course, this is not an excuse for bad judging or unfair motions.) 
5. Be intellectually curious.  Regularly read interesting non-fiction outside your own academic specialty, and do so with a critical eye.  This will do two things; most obviously, it will increase your general knowledge, which is helpful in itself.  Equally important, however, is that it will train you to think deeply about how arguments work.  You can reflect, with all the time in the world, on whether you agree with what you're reading. You can parse it carefully, and test it for subtle weaknesses or fallacies.  Debating requires you to make good arguments quickly.  But it is easier to do so if you have a wide experience of different forms of argument; different persuasive strategies, and their strengths and weaknesses.  Learn first to make arguments well.

I'd add as a final caution:  Be patient.  When you've a strong grasp of the basics of debating, progress ceases to become gradual.  Anecdotal experience suggests that most debaters find that they plateau for moderately long periods, and that improvements arrive quite suddenly and drastically.  Frequently, one missing skill from your debating skill-set prevents you from using other skills as effectively; for instance, finding it difficult to listen in the last minute of your opponent's speech makes your rebuttal connect less well, which in turn undermines your confidence and poise...  Realising what's holding you back can frequently lead to apparent improvements on many fronts.  (What I'm saying is that the production function for good debating is typically multiplicative rather than additive, so that different production inputs are complements.)

At the same time, the timing of these sudden improvements is, to a large extent, within your control.  You can affect whether your plateau period is counted in weeks, months or years.  Good teams are always striving to improve themselves; they learn quickly from their own mistakes, and frequently can reap greater dividends from a single competition than worse teams can from a whole season.  Improvement doesn't just happen by dint of the sheer number of debates you've done; it takes careful self-examination and critical thought to become excellent.