Solstice

Oh hi! This sort of thing falls under my special interest, so I have some tips I've compiled over the years, both from personal experience and others that know their stuff — I hope it can prove useful to you, or anyone else reading this! Obvious disclaimer that everyone is different, and I'm also an AuDHDer specifically, so mileage may vary. Experimentation is always key. That aside,

• Always start small. This is where a lot of people stumble. Focus on building one routine at a time, and try not to pack too many new things in at once. 1-3 tasks is the sweet spot. Even if you have some habits down individually, stacking them on top of each other all of a sudden can be overwhelming. It may feel tedious, but no one can go from 0 to 100 in the blink of an eye. Feel things out and take your time!
• Prioritize. Especially when you're starting small, there's not room for everything you'd like in your dream routine, so it's important to figure out what's most essential for your health and wellbeing. Dental hygiene is a standard vital to health. Getting dressed is also a solid option assuming you don't live in a nudist colony, but no judgement here. Apply prioritization to which routines you work on first as well, figure out which ones are most integral to your day running as smooth as butter.
• For a lot of people, this tends to be a sleep/wind-down routine, so that may be a good place to start. Sleep hygiene is important and your day truly does start the night before! Like you obviously can't wake up at like, 4am if you're awake until 2 binge-watching video essays night after night. Or you can but it will suck ass and you will hate yourself massively. If you're very particular about your wake-up routine, start making room for it with your sleep routine.
• Furthermore, I think it's really helpful to create routines for different energy levels/time restraints. What's your bare minimum? What about living deliciously? What about the midway point in between the two? There's going to be days you wake up late, or drained, or something else goes wrong and the rain makes you cut your parade a bit short. Having adjusted, set-in-stone routines you can still follow to accommodate these days will help you keep much-needed structure in chaos and help you to not feel discouraged when an obstacle comes up. Especially when starting small from square one, these variations can be easy enough to create, too.
• Give yourself buffer time! As much as possible! You are not a machine that can jump seamlessly from thing to thing even on your best of days. Neurotypicals can't do this sustainably either, but throw in a dose of time blindness and the ability to get distracted by literally anything, and it's even more unrealistic. Again, you want to account for this and avoid discouragement. Your mind is going to wander a little bit when you brush your teeth here and there. You may lose the occasional 20 minutes looking out the window. Guestimate or note how much time a certain tasks will typically take you and double it to be safe in order to plan to the best of your ability.
• Take advantage of trigger habits. These are small, easy things you can do that serve to create momentum in your routine, or one specific part of it, like a domino effect. A lot of times they function like a signal that just hits a certain switch in your brain. Turning off your computer or putting your phone in a drawer in the evening may be your trigger habit that tells your brain it's time to start getting ready for sleep, and makes it easier for you to do whatever else is part of your wind-down routine. Morning stretches or making the bed are common as a wake-up alarm, and they get you through the herculean task of getting out of bed so you can do other things that may not feel as luxurious as extra snoozing. The best type of habits to do this with are anchor habits, core routines that are already formed and deeply ingrained in your life. This could be waking up, or eating a meal, things all of us do; or even something like jogging, if it's become second nature to you. Use these as focal points, a foundation to build new routines and habits off of.
• On that note, if you have trouble initiating one particular task, set up a trigger for it. Usually that's the most stupidly easy first step you can break it down into. For example: If brushing your teeth is difficult, then don't see it as one whole task you have to cross off your list. Start with the very first step of grabbing the tooth brush and wetting it and focus mostly on that. When I used to struggle with this back before my electric toothbrush bc sensory issues, and that didn't work, I used a analog timer to set an alarm instead. Doing that was even easier for me, still worked to send that signal of "hey it's time to start this" to my brain even though it wasn't actually a part of the task at hand, and then I had a clock to race against which added some novelty and fun.
• Point! Of! Performance! All the steps you have to take to do something can quickly add up and make that task much more difficult, especially with your brain already lacking in the executive functioning department. Friction builds up quick and the more there is the more your brain gives less of a shit about what you're trying to do, especially when as far as it's concerned, there's better things it could be doing that feel much more immediately satisfying. To fix this, you want to simplify your life and streamline everything as much as possible to cut down on unnecessary steps. If you like tea or coffee in the morning, make sure everything you need including your favorite mug is all in one place, the less cabinets and drawers to open and steps to walk the better. If you want to workout more, keep all your equipment, your clothes and/or gym bag in one place ready to go when needed. Not only does this make doing these things generally easier, but it also helps to cut out distractions since you won't be wandering around as much. Eliminating decision fatigue can also be a huge part of this. Pick and lay out outfits, decide on your meals and morning drink the day before, if you can. Making these decisions first thing after waking up can be more taxing than you might think.
• ALSO! You can use point of performance not only to do more of the things you want to do, but also less of things you don't. I have my eBook program and Obsidian on my task bar to better encourage me to read and write since they're right there. Sometimes I'll even open them accidentally and decide I might as well. Chrome and Firefox however stay on my desktop, and for things I need less often that can be distracting, I have to go through my files to access them.
• It can be helpful to journal as you build your routine and experiment. Note any hiccups, things that went well, how you feel about the things you do or things you try or want to try. This will help you prioritize better, align your routine better with who you are and what you want out of life, and when a problem does come up, acknowledging it on paper can make it easier to problem-solve and find a solution (assuming you decide doing so would be worth it.)
• Use mindfulness to really create a connection with, and learn to enjoy, every part of your routine as much as possible. Food and drink are the popular, most obvious choices to delight in and soak up, but there's so many other things we do as maintenance, and because we're supposed to, and we don't fully appreciate them. We have an interest-based nervous system. Discipline only takes us so far. To close the gap and obtain the motivation we need to thrive, we have to find as much pleasure in our routine as possible by focusing on how we feel after and during every step.
• This is also another point where starting out small, and taking things slow and steady comes in handy. For me, washing my face was one of these obnoxious maintenance sort of things. I love skincare. I knew I much more enjoyed my face feeling clean than not. I knew the long-term benefits were great and worth it, logically. However, while a neurotypical brain gets a little chemical boost from looking forward to the future when it comes to these small tasks, we don't tend to. My brain didn't really seem to appreciate the whole ritual of soaking my whole upper body every morning without a sense of instant gratification. The cleansing process felt good, but not worth it enough to create a true desire to engage. Until, that is, I started meditating afterwards, and gave myself the time and space to really bask in that fresh-faced feeling. Now, I have to rely on discipline a lot less to wash my face because I just naturally want to feel good again.
• Finally, and this one is more specific and less general, writing notes to save your progress is a really fantastic idea here, and one I'd highly recommend prioritizing! Not only does it ease the friction of restarting what you're working on at a later date, but it helps you neatly tie up any loose ends before you set it down, so your mind has less information to cycle through and fixate on. It's a bit like decluttering your desk here and there. A good old fashioned braindump before relaxing or winding down for sleep is also extremely helpful.

That's all for now lest I write a novel, but I think these are the most important things to keep in mind and start out with. When it comes to setting aside distraction time, that's a whole other can of worms that can be healthy or tricky based on many factors and it's hard to dive into without knowing someone's exact situation. But for me, I find it's better to not really fret over it, and I'd worry the "distraction" label is already starting off on the wrong foot due to the negative connotations. Small things like that can wreak a surprising amount of havoc on your mindset! It may be better to just let go of it a bit and more gently give your mind time to wander during buffer periods and scheduled free-time (And of course, limits on things like social media here and there are healthy, I just find it's better to have them in general and not push them into certain time slots.)