I'm going to invoke one of my favorite quotes, and then go meta:
There is nothing so useless as doing efficiently what should not be done at all.
-- Peter Drucker
Just what is it that you are trying to be more productive at doing, and what do you hope to gain from it?
To summarize, my to-do list is long and heterogenous, and most of the items on the list are there because I think doing them will improve the chance of a positive singularity (some through just a few levels of indirection, like volunteering for SI; some through many levels of indirection, like watching sped up video lectures in order to add to my conceptual toolkit).
Have you tried using implementation intentions they seem like they have good research backing. See this , and this
For bystanders, I previously recommended kratom, which is probably one of the most interesting drugs that is legal in the United States, to gwern as a way to enter a highly motivated state. For me it seems to act as an ugh field off switch. You can buy kratom from an online store run by a Less Wrong user.
To answer your question, it's not something you want to be using more than a couple times a week, and recently I've been experiencing some digestive problems (unrelated to kratom) which have made me reluctant to consume anything that isn't food.
For digestive problems of all kind, I recommend supplemental enzymes shortly before meals. In some people, they work better than more harmful or complicated or expensive medical interventions. http://www.amazon.com/Super-Enzymes-Now-Foods-Tablets/dp/B002FK1NJA/ref=sr_1_3?ie=UTF8&qid=1331024844&sr=8-3
If I feel generally energetic and motivated, think of the most important, intimidating task I could possibly do and work on that. (...)
Frequently, I'll work on some kind of longer-term intervention to increase productivity, like learning about and implementing some new productivity system. Of course I'll eventually abandon the system, but it will provide benefits until then.
This strikes me as... unhelpful. Your chief use for motivation, apparently, is to increase your future motivation. I suggest that this is not the way to get things done.
I find that on average, it seems a new system produces benefits that exceed the costs necessary to institute it. Kind of like how in glycolysis, ATP molecules are required early on in the pathway, but the process eventually ends up getting you more ATP than you started with. (One of the few things I remember from ninth-grade biology...)
That's good input though; I haven't really been scrutinizing to check to see whether interventions are paying for themselves.
Although it certainly seems that over time, one could learn how to make interventions more persistent, or what kind of interventions tend to be most cost-effective.
Lately, I've been in a months-long motivation slump. This has given me the opportunity to gain a few insights about how to get more done with less motivation:
In general, I've noticed that my self-improvement efforts seemed to go better if I see my own behavior as inherently chaotic and try to work around that.
I've come to realize that aiming for a grand unified system for how I do everything doesn't seem to work very well, and even if such a system actually is a good goal, it would be better to design and implement it piece by piece so I could gradually test my ideas against reality. Embracing scrappiness doesn't fit very well with my perfectionist personality, but fortunately I have another part of my personality that thinks it's silly to avoid doing what works well in practice.
Please share your productivity tips for those low on motivation in the comments.