Planning
Organising
Lists
Structure
Pattern
Do the same things on the same day. I.e. we have our shopping delivery not only the same day, but the same time slot. Normally buy the same things, just take the list we bought the week before and "tweak" it slightly for any minor changes we need. Makes it so much quicker. We have usually the same kind of meal on each day, i.e. Tuesday is Pizza day, Thursday is Pasta, Friday is fish, etc. Meal planning saves so much time and money.
We have rigidly defined roles. There are things I look after and things OH looks after. We rely and trust each other to do our respective "jobs" so we're not duplicating or getting in eachother's way, nor checking up on eachother or contradicting what the other has done.
The house is organised. Things are put away in specific places. That way, there's no wasted time looking for things. Putting stuff away in it's place takes no time at all if you do it as you go along. Neither of us would think of going upstairs without seeing if there's something to take up, such as ironed washing, towels, bedding, etc., No point making a special journey to take things up when someone may have been going up empty handed. I often do the ironing whilst watching TV rather than "wasting" time on it. Whoever is around will hang out the washing and then bring it in again - we even trained our DS to do it without us having to tell him, i.e. if he notices it starting to rain, he automatically looks to see if there is washing out, and will bring it in!
When any of us notice something has run out or running low, we write it on a "to buy" list in the kitchen, so it gets bought at the next convenient opportunity.
We also "manage expectations" whether for Christmas/birthdays, holidays, days out, etc. We have always told our son exactly what is going to happen, sequence of events, etc so he's never caught out by any surprises.
Eating meals together makes the World of difference. We don't "formally" dine at the dining table every meal, we do sometimes, but we also eat on our knees, etc - but we make a big point of doing it together, even if we're otherwise engaged watching TV or DS is on his ipad - it's the opportunity to have a family chat about forthcoming plans, events, etc.