Things which have a deadline are much more likely to get done on time than things which don't. So one way to improve timeliness is to set deadlines. A schedule can be very helpful.
Things which are in your control are much easier to do on time than things which are partly or wholly out of your control. If you have to wait on someone else, it doesn't matter how good you are at keeping up; they can still make you late.
Inaccurate data will screw you. If a recipe purports to take 20 minutes to cook, but is still raw then, it's not your fault. However, you should take note of the required cooking time for future reference.
Unpredictable things will screw you. If a quiche sometimes takes 60 minutes to cook and sometimes takes 90 minutes to cook, it's likely responding to obscure variables (e.g. humidity) and will be difficult if not impossible to predict.
If you pay attention to how long it takes to do something, you will learn over time, and get better at both estimating and completing tasks. If you do not pay attention, you will not learn these skills, and will continue to run late and be frazzled and not get shit done.
Make sure you are setting appropriate goals for the time, energy, and other resources available. Trying to do too much with too little is a common cause of failure. When your schedule is full, say no to more. If you don't have the power to do this, it is not your fault for running late, it is someone else's fault for overloading you.
Set aside time to work on things. Just showing up to do the work can make a big difference. A lot of things don't get done because people skip this and try to cram them in at the last minute. It is often more effective to set a task for "spend one hour weeding the garden" or "weed the row of carrots" than "weed the garden."
Pad your deadlines. You know that things often take longer than expected, due to problems cropping up. A bus is late, the printer runs out of ink, etc. Plan for this. Think about how much you honestly expect, and how late things often run. Add 10-20% for a small, simple project and 50-100% for a long, complicated project. If you get done early, that is much better than late.
Do not lie to people. If you're running late, say so and recalculate. Pretending you're not running behind when you are just makes matters worse. And if you're in charge, never scream at people for admitting they're late or they won't be honest in the future. Recalculate and move on. Bitching just wastes more time.
Be aware that some jobs are never done. Housework, yardwork, childcare, writing -- there's always more to do than you have time for. First, prioritize. If you can't do everything, concentrate on the most important tasks. Second, define portions small enough to finish. Do a load of laundry, pick up an armload of sticks, etc.
Include firebreaks when nothing is scheduled. This is critical for events, but also reduces the risk of overruns and burnout in everyday life. If you schedule everything back-to-back and one thing glitches, it will knock over everything after it like a row of dominoes. A firebreak in a domino run is a space with no dominoes so one goof doesn't ruin the whole run.
If you get stuck, really stuck, don't beat your head against a wall. That just wastes time. Do something else for a while. Come back to the problem when you are fresh. You may think of a different solution then.
Understand that these skills are work and burn energy. If you do not have enough energy, stuff will not get organized well and probably not done on time. So do your organizing when you have the most energy and best focus.
Sometimes a break can help refresh and refocus you. Get a healthy snack or drink. Visit the bathroom. Do some stretches. Take a walk. Learn what helps you.
Were you taught how to do these things? Some people were, others weren't. If you weren't, take time to study and practice them. There are books, classes, and specialists for this. Or you can just ask your friend who is never late and uses spreadsheets to organize everything. It's not magic, they're actually doing things differently, and at least some of that is probably stuff you could learn.
Bear in mind that many things impair executive function -- mental disabilities, many drugs, lack of sleep, poor diet, insufficient activity, chronic boredom, inappropriate tasks, noise, illness, head injury, etc. Remove as many of these as possible. For things that cannot be fixed, study how they affect you. Sometimes extra time or tools may help you compensate for these limitations. Do not beat yourself up if you can't exceed your limits. If you are really terrible at it, despite working hard and trying to learn the skills, consider arranging your life to minimize this type of work. Prolonged Adaptive Stress Syndrome ruins lives and health.
Considering the topics:
1. Coding: any coding task for research or schoolwork (e.g., analysis in Python).
Factor time to compose the code and time to debug it. The latter is especially difficult to predict.
2. Writing: any writing or editing-focused task (e.g., working on a paper draft).
Break this down into steps. Collect resources, make an outline, write a rough draft, and polish it. Do major structural editing, then line editing, then proofreading. Time yourself working so you will have some idea how long it takes to write a page, or 10,000 words, or whatever. Do not guess.
3. Reading: any reading-focused task (e.g., reading a journal article).
Just sit your ass down and read the thing. This is entirely in your control, unless your schedule in general isn't. If you need to think about or remember the material, plan to read it during your most alert time of day. If it's long or complicated, you might need to read it in sections, look up other references, take notes, or read it more than once. Know your reading speed!
4. Administrative: any task related to running a research group or department (e.g., organizing meetings).
You are probably just screwed, because this always involves other people. But you can try:
* teaching them organizational skills
* making sure someone with high executive function heads each team
* sending reminders (this really helps for meetings and other appointments)
* using a shared schedule with a paper or electronic calendar
* discussing or posting each day's main events in the morning.
5. Talk Prep: writing or practicing a talk or poster presentation.
Just do the thing. Practicing is literally nothing more than picking a block of time and reading or reciting the stuff until your timer goes off. For writing, see above re: breaking it down into steps.
6. Service: volunteer work (e.g., organizing outreach activities).
If it's volunteer work, you sign up for a block of time and you hand out soup or build houses or whatever.
If it's organization then see above re: Administrative.
7. Problem Set: homework for a class that is not coding- or reading-focused.
This can be extremely difficult to estimate, especially as assignments vary in size from one day to the next. Options include:
* Time yourself and use that to estimate.
* Divide your available study time by the number of classes or assignments. When you run out of time on one, stop, and move on to the next. That way you don't waste it all on one and get none of them done. At least you'll learn something in each.
* Sort your assignments in priority of most important class first, or class you can't afford to flunk first, or some other method. Work on the top item until done, then the next, until you run out of time or tasks.
* DO NOT short yourself on food, sleep, or other survival needs. You won't learn much anyway if you're fucked up.
Miscellaneous tasks rely on generalized timebinding skills.
* Time how long it takes you to do stuff.
* Schedule times to do things.
* Use cognitive offloading (calendars, timers, etc.) to free brainspace for work.
Here are some resources:
A Guide to Executive Function Skills in Adults
7 Signs of Executive Function Disorder in Adults
Resources for Adults With Executive Function Disorder
How to Improve Executive Function Skills
How to Be Punctual
14 Essential Tips for Meeting a Deadline
4 Ways to Estimate How Long a Task Will Take
How to Get Better at Estimating Time for Tasks
How to Stop Dealing With Someone Else's Lateness
The 59 Best Organizational Tools to Enhance Your Work (computers)
42 Essential Organizing Products For Your Home (materials)
Day Designer Free Printables (organizer pages)
25 Awesome Tools for Getting Organized (miscellaneous)
Getting shit done is a skillset. Organizing things is a skillset. If you don't practice, you won't get better. But don't beat yourself up over things outside your control, and if other people do, file them as abusive idiots and work on escaping them. Your responsibility and authority should always balance.