Have a couple of ‘go bag’ pouches with essential toiletries, makeup and personal bits (chargers power banks, tissues etc) to reduce mental load. I’ve seen the Space NK ones online but am sure you can get cheaper multipacks on Amazon etc. Clear bags are a lifesaver
Buy multiples of stuff like phone chargers - keep one in car, one in handbag, one in work bag etc
If you take meds, wear contacts or have any health needs, tell your GP/pharmacist/optician and stock up on extra meds and lenses if you can safely do so
Invest in your luggage - I like Beis, North Face for rucksacks and you can’t beat a Longchamp bag (with inner organiser). TMMaxx have good luggage. If flying a lot get a small hand luggage sized bag that you know will fit on all airlines (though I like a PPs suggestion of insisting on the highest class of travel/best service possible)
Invest in good shoes and jackets - will always be comfortable and smart
When you get home unpack and do washing immediately or invest in sending out your washing, ditto meal prepping for freezer or getting in some healthy quick options when you get home. Automate as much as your life at home as possible during busy periods, if you have a partner at home that’s the time to rope them in or come up with strategies to cope
Think of time vs money - especially if you are booking your own transport eg flying in at 3am may save money but you will be shattered and paying over the odds for a taxi
Get a lightweight reusable water bottle and coffee cup - I like Stojo for portability and take some cutlery with you
Get some hand wash solution and stain remover you can take with you
Try and keep to healthy habits and get out of the ‘holiday’ mindset - but do treat yourself once in a while!
Download lots of audiobooks/podcasts and get some good books/crossword or sudoku books for downtime so you don’t end up scrolling. Esp for public transport. I try not to be on my laptop unless completely necessary - maybe get a bit of work done in the airport lounge but don’t feel the need to optimise/monetise every second of your day. You are human!
Don’t feel too guilty about not seeing friends/relatives in the area if you are too knackered or genuinely can’t fit it in. On the other hand it is a nice way to catch up with people who live further away
Have a dedicated little pouch for receipts or try and get digital receipts where possible. Take photos of receipts when you get them and file all claims as soon as you can
Avoid paying out of pocket wherever possible
Slightly contradictory to my earlier tips but learn to pack lightly and quickly
Settle into your room as soon as you arrive and try and schedule in some downtime for yourself especially if you are client facing most of the time
Have a checklist by your front door of your essential bits but eventually it will become second nature
Enjoy the ride!