Heres a list of things to avoid that look sus! (compiled from many other posts and lp reddit)
Getting out of the car and putting on a backpack
Covering your face as you walk in the door
Looking at people, not merchandise / noticing every person who walks by
Looking at people instead of looking for a cart when they first walk in the building.
Selecting a hiding item (trash can, tote, large box) and placing it in the cart before going to a high theft area
Women who put their purses in the top of the cart and leave them open. Then when they select, some things go into the basket and some go next to the purse.
Out of season clothing (sweatshirts to body-pack in the winter etc.)
Hoodies on especially if the drawstrings are pulled
Leaning on the cart when pushing it (elbows on cart to look relaxed but has a stiff back)
Going to the bathroom multiple times
Covering your mouth (sign of anxiety)
Looking around the store at an abnormal rate
Being surprised when an SA approaches you
Removing hangers from clothing and leaving those hangers on the rack.
Hanging around blind spot areas too much
Picking items w/o even looking at prices
If they came inside the store on foot (walked instead of drove)
Walking with TOO much confidence / a cocky demeanor