Always have a hand free to grab a wall or railing or anything stable and nearby.
If you can't have a hand free (ie when carrying a large pan of food) try to lean on something with another body part (ie your hip against the railing of the stairs).
When standing in one spot it is a good idea to brace yourself with your feet or hips against a solid object.
If you are brave enough to sit on a chair in the salon (vs the bench) the hand free rule still applies and you will want to sit with one leg braced off to the side.
If there is a big roll stay still till it passes. This may involve moving down the deck in three short trips instead of one continuous one.
Waiting for the roll applies doubly on stairs and extra on stairs that have a 90 degree turn part way up.
Doors must always be latched or in your hand or they will inevitably fly open and crash into the wall. This applies to cupboard doors as well.
Be prepared to switch the "head" of your bed often. Perhaps nightly, perhaps during the night. The key is to have your head on the windward side of your bunk if you are sleeping thwartships. If your bunk is fore and aft wedge yourself in with pillows as best you can, the less space you have to roll in the better.
Get used to sleeping through rattling, creaks and groans, footsteps above your head, banging and the roar of the generator.
That said make sure all your things are sea stowed as that pen rolling back and forth in your cabin will be enough to keep you awake. Also note trying to sea-stow said pen at 2 am is not likely to be successful.