Any human can be trained if you are consistent and keep it simple. If your human is a slow learner, try to be patient. A poorly trained human is a pest and an embarrassment.
Cat Talk by Cleo: How To Train Your Human
ESTABLISH THE GROUND RULES
The Litter Box
Never use a litter box unless it is clean. If there are any smelly clumps in the box, go pee in her shoes. Do this three times in one week and I promise you the problem will be solved.
Make your feelings known at the very first meal your human tries to feed you. Warily sniff the canned or dry food she has set down. Do not eat a single morsel. Raise your left front paw and shake it in obvious disgust. Walk out of the kitchen more in sorrow than in anger. Repeat every mealtime until your human understands that only freshly minced wild salmon is acceptable.
Decide which bed is the softest, warmest bed in the house. That'll be yours. Chances are you'll have to share it with your human. Train her to go to bed at your bedtime. This will set the tone to help her understand who gets to pick her spot and who has to accommodate. Personally, I recommend the pillow.