N is for Next.
You've just finished one of the tasks on your list. What is the next thing you need to do? Don't worry about whatever comes after that, or reviewing your entire to-do list each time you finish something. Review once, order the list, then bang-bang-bang work through it. You've already worked out what comes next, so when one item is complete, just move onto the next.

Otherwise you'll end up worrying about the order of things, and procrastinating by dithering over what your next task should be. When you're going back to the list isn't the time to decide on the order - that's something for when you're taking a step back and looking at the bigger picture. Once you're working through the tasks you're just cranking widgets; the thinking about task order is done.

You might succumb to trying to cherry-pick tasks, and start a number of items in succession without fully finishing any. I find that when I'm in that frame of mind it's because I'm resisting getting properly stuck into things, and am looking for something easy. Usually there isn't anything easy, and so I wind up trying a series of tasks but don't make any headway on any. All my effort is wasted in switching between tasks rather than in finishing one.

This is one of the big advantages to getting all the things you need to do out of your head and into some exterrnal system (a sheet of paper, a notebook, to-do list app...). If your tasks are in a system that you trust, then your brain won't keep thinking about it in order to remember it, and you're less likely to get distracted. If your system lets you keep things in multiple project- or context-based lists then even better - you literally won't see the other items that you can't, or don't want, to deal with right now whenever you look to see what's next.

Making lists isn't the key to being more productive. The key to being more productive is using lists to let you get the right things done at the right time, as quickly as possible. By all means review your list regularly to make sure that you're attacking the right tasks, but anything more than a couple of times each day is too often. Once you've done the review, the only question you need to ask from task to task is "what's next?"