On average, most shots in film are about three seconds long (about 72 frames). There are shorter shots, which are usually easy to deal with. Then there are those that are much, much longer, that can become quite daunting to deal with.
Here are some methods I use to tackle these shots and make them a bit more manageable.
The big thing is focus. Like so many things, breaking down tasks is very helpful when it comes to a long shot. I do this both in my scene and organisationally.
When working in Maya I will limit my timeline to 100 frames, even when blocking, and actively ignore whatever is outside that range. As I go through and become happy with that section, I don't go to the next hundred frames. I overlap about 20 frames and start from there. It quickly brings that daunting length down from, "I don't know how I'm going to do that," to, "I'll get to that in due time." One of the benefits of this method is when you loop 100 frames it's easier to spot mistakes. Similarly, in splining and final polish, isolating a leg or arm in the hundred-frame fashion really helps the mistakes stand out. That said, it is important to, every now and again, look at the full length just to make sure it's still working (and to make sure nothing's been ruined!). It's important to avoid tunnel vision and lose sight of the shot as a whole
All the tips I put forward in the Keepin' It Tidy post will go a long way toward making a long shot more manageable. All the myriad of ways to get a fresh look at your animation (flipping, flopping, inverting colour, etc) will be hugely beneficial as you make your way through your shot.
Outside of Maya I make checklists. Sometimes in my notebook, but more often than not I use Google Keep. It helps organise my thoughts and focus my workflow rather than randomly jumping from task to task. There is a nice sense of accomplishment when you check things off and find the list growing shorter. I tend to divide up by character and have the related tasks underneath. These start out broad, such as "do a facial pass," but as time passes they become more specific.
At work, I'll write these things down as I commute home on the Tube, ready for the next day. This will usually include notes from dailies, things I need to hit, and things I still feel I need to do.
The long and short of it is that there isn't a script or anything that will make a long shot easier. It's about being deliberate and methodical, compartmentalizing your animation down into edible, easily digested chunks.
Keep on keyframing!