Be productive not just busy.
Millennia-old Yoga Sutra Of Patanjali is still the most relevant (how else could it be, if human physiology haven't changed since then) text on the subject.
Yoga is a way (a methodology) of gradual self-transformation to attain an optimum balance (a near-perfect, animal-like adaptation to the environment which evolved it) by changing one's habits - unlearning being a busybody and acquiring the proper habits of being what you really are (according to What Is) - an evolved animal augmented with a language (and therefore abstract thinking).
There are universal preliminary practices which are basically about a process isolation (you) and using proper training set (information hygiene) for your neural networks. And, doing the right thing, of course.
It is rather ironic to see how an ancient wisdom boils down to backtracking search algorithms and supervised (by the environment via feedback loops) learning. Yes, we are merely adaptive biological machines, you like it or not.
Being a part of social system is good only when you literally are a specialized cell of a social body. This is what social (and economic) specialization is all about - a social contract.
If, however, you are an inventor, a writer, a producer of a product, everything social is your worst enemies.
So, the first principle, the first preliminary practice is to get out of society as much as possible (which is costly).
Isolation is not optional, it is required. Cells themselves are isolated pieces of an ocean. The membrane is what defines them.
Food and exercise
To do intellectual work one have to be physically healthy. This basically means to avoid distractions to your mind from your own body. A healthy body is being forgot by mind does not remind of itself. Invest in natural food and cardio.
The main function of a cell's membrane is to filter almost everything out - everything toxic, harmful, unnecessary, distracting. This keeps a cell from being overwhelmed with outside bullshit, literally.
A cell has highly specialized (by literally doing pattern-matching) "pumps" which pump in glucose and other nice things it required to function.
It has receptors (binding sites) for certain distinct message-molecules which triggers certain sub-processes within a cell, which is the major way of asynchronous communication within a body (a system).
Distraction of attention (social bullshit, rumors and memes are literally viruses) is as harmful as toxins and real viruses made out of pieces of DNA in a capsids (yes, even viruses had a membrane).
You have to develop your own "membrane" (and "receptors") to keep social bullshit out. In computer systems an OS (or language's runtime) does the filtering.
One thing at a time
This is the essence of Zen practice - whatever you do you do with a whole of you - like small children or animals do.
You cannot multitask. Well, you could easily (to some extend) multitask a several physiological and one mental activity (as long as everything goes as evolved). Have a trouble breathing and everything else vanishes from your mind. This is "by design".
Zen Mind is about putting your whole being in what you do. It is an extreme focus, an opposite of multitasking and this is the right way.
Partition your time
Partitioning is a fundamental and universal principle. It is deeply related to evolved systems of nature we call organisms.
Partitioning of time means that you are literally reserving chunks of time for doing one single task without interruption, without any distraction.
Prioritize and schedule
Make a list, sort it according to priority (or weight). Traverse from highest to the lowest weight.
Weighted sorted lists (and weighted sums) are the most fundamental analytical tools.
Everything is achieved by doing, but to do it one have to develop self-control. Have you skipped the morning run again (yes, I did)? This is lack of self-control.
Discipline is what develop self-control. It is just a regular, habitual exercise of changing a wish to a will.
These are mental tricks to prime and trigger your wishes. A picture of a Buddha is a reminder and a motivator.
A piece of code printed on a wall (instead of a sutra) could be as good as a Muslim inscription in Arabic letters. It just works (this is precisely why these things still exist).