Today, I wanted to talk about work processes and productivity. I'm not exactly the best metric of this (though I have been writing a couple thousand words a day on average recently, so something's going right). As people probably are aware, I work on tabletop RPGs, and there's a survey going around asking creators to describe the processes they use as they work on their games.
Some of what I do may be useful, some of it might not; it's a personal process, though I've read a fair amount of the literature (though I'm plenty willing to ignore it).

Get Comfy

The first thing I do when I'm going to work for any extended period of time is get comfortable. Even if I'm planning just a short burst of work, I'll make sure that any potentially distracting tasks are taken care of (e.g. hitting the bathroom, eating an upcoming meal, checking for messages on my phone), then be fully prepared to work.
This prepares you in two ways:
First, you're trying to push yourself to peak performance, and if you're doing creative stuff that typically means putting yourself in a decent mood and getting everything ready so you have a positive outlook on the work you're about to do. I'll drink a cup of tea, put on some music, and, if it's a cheat day, have a treat that I won't normally allow myself on my diet. I try to stay hydrated too, since that really helps improve one's ability to work.
Second, you're avoiding disruptions to flow. Once you're half-way through writing, you don't want to have to get up to hit the bathroom, or check your email, or do other things. I don't actually find this terribly disruptive, since I'm usually pretty business-like, and I'll often start a short-burst of work and then figure out what's hurting my productivity, fix it, and return to work.

Get Organized

I'm now meticulously organized with my time. My main method of doing this is on Habitica which I find has a great combination of gamification and organization.
This is actually something I struggled with for a long time, but as I've gotten even just slightly more organized I've managed to both remove distractions. For instance, I always check my work email at least three times a day; before work, at noon, and around dinner-time. Once I've done those three daily checks, I cut myself off, so the only time I see a work email is if it pops up on my phone, and I'll happily ignore it until my next check-in.
One thing that I find helpful is having certain daily goals: "I will write X today." or "I will read a chapter of a novel today." This both helps with the first step of my process (getting comfy) because I don't have to deal with distractions and I've prioritized tasks that help me get into the mindset and physiological conditions for flow.

Ready, Aim, Fire

My work method can be summarized as a rocket-propelled chainsaw in a forest. I find something, and I just work until it's done. There is something to be said for this, and a few disadvantages. I don't prioritize any one task: I find that my work tends to be interconnected (for instance, writing for daily posts tends to give me ideas for my other work) so there's no harm in going between tasks.
Another thing to note is that once I'm in flow, I avoid any task that disrupts my concentration. I might get up to have a glass of water, for instance, but since I'm primarily engaged in creative endeavors and my mind wanders freely regardless of what I'm doing with my body, I'm pretty safe to do that. The degree to which you can pop between things without losing flow is probably a product of enough factors that you might not find that this works for you.
However, whatever I do I devote my sole attention to, whether it's for two minutes or an hour. When I'm feeling particularly hardcore, I'll turn off wi-fi to minimize distractions further, but I only do this when I feel like it. I reward myself on Habitica when I do, which strikes a nice balance between the willpower required and the downside of having to deal with all the assorted issues that come up when you don't have internet going (streaming music is a blessing and a curse).
The number one thing that I find helps me pick up where I left off is identifying issues clearly. When I'm working on a game, I choose an element of the setting or a feature I have not yet worked on (or which needs editing or alteration) and then start writing there.

Don't Waste Energy

I'm heavily inspired by the Pareto principle, and avoid wasting energy wherever possible. This means that I shift tasks a lot; I'll write for two or three minutes, hop off to something else, and come back later.
Of course, I've also developed a fair amount of stamina and resilience, so I'm able to stick with one task for a fair amount of time (for instance, I write most of the pieces I post in a single sitting, or otherwise a sitting that I then interrupt to balance out issues disrupting my pursuit of flow).
20% of your energy brings 80% of the results, so you want to plan on working for a fairly short amount of time, and intentionally make sure you're pouring out that energy where it needs to go. If you are applying the right energy to the right places, you'll find that you achieve double or triple what you were previously doing without too much issue.
You also want to make sure you don't spend more time than you want on a certain task: for instance, I review languages for fifteen minutes a day if I'm currently studying them and I'm stuck dealing with a busy day (and between my day job and my writing it's pretty much always a busy day).

Vilfredo Pareto, image courtesy of SIE-ASE

Work When You Feel Like It

One thing that I've forced myself to do is to listen to my own demands more closely as I've been working on my productivity, and I've found that it helps a lot more than you think. I started a diet recently, and I've been struck by how much less hungry I feel.
Working can be like that too. I used to force myself to use morning time to write, but when I'm on a more disciplined schedule I often revolt against that. I'd still write in the afternoon, for instance, but I'd begin my day frazzled and unprepared.
So I shifted most of my writing to the afternoon. To my surprise, my net output increased. I still write in the mornings–if I feel like it–but moving my productive tasks from the realm of necessity to the realm of desire is something important.
It is important, however, to keep in mind that as with dieting you can't be controlled by your whims. Your emotions possess powerful subconscious awareness of your condition. If you don't feel like working, it's probably because you have other needs to meet right now.
And people have a psychological need for leisure and play (says the game designer). You want to give yourself that time.
However, to stretch the diet metaphor, you want to watch out for what you are doing in the leisure time and how you are doing it. If you are doing something that reduces your ability to re-enter flow later, or if you are spending so much time on leisure that it becomes a rote behavior that has failed to yield results (again, Pareto principle) you're going to be miserable.
The counter-point to this is that you should–must–provide yourself with a reward for work. I have a box of Swedish Fish sitting on my desk (a gift from someone who doesn't know I'm on a diet) that I can eat if I earn 100 gold on Habitica by doing work. To enjoy that sooner, I have to stick to my diet, get work done, and engage in positive social activities that I tend to prefer avoiding.

Wrapping-Up

To hit peak productivity, I do four things:
I intentionally put myself into a physical and mental environment that encourages flow, including organizing my future tasks so that I won't find myself without something to do if I finish.
I spend exactly as much time on task as seems to be productive and fruitful. Since my primary task generally involves writing or otherwise making content with measurable outputs, that's pretty easy to assess and doesn't take a lot of time.
I obey the Pareto principle to delegate energy to tasks that I am able to best complete at the current moment.
I rely on rewards and self-discipline to foster an attitude that leads me to work productively and recognize when my mind and body are primed for work and when I need to do something to get back to flow.