I was gonna put this in the tags but I decided it's too important, as someone who has worked food service and has also never once gotten food poisoning:
Warm + long periods of time = bad. A lot of people very casually leave leftovers out for several hours or overnight. When food is roughly a little under room temperature to about just-before-too-hot-to-eat, the rate of bacteria growth doubles. For some foods, even thirty minutes at this temperature is dangerous. An hour most certainly is. You need to keep your leftovers out of this range. If it's not too hot or too cold for YOU, it's also comfy for bacteria.
Do not pack hot food into a large container and then put it in the fridge. The middle will not cool properly and will stay in that danger zone for too long. Either pack it like a little donut, put your container in an ice bath and stir until the food quickly cools down, or pack it into thinner containers.
No amount of household mold on food is safe (unless it is cheese that is SUPPOSED to be moldy. I don't mean a yellow cheddar that has started to mold. I mean like specifically moldy cheeses - these are grown with special cultures of safe mold, not just any mold). You can't get away with cutting mold off of your food. If there's mold on it, it has already spread through all of your food. Throw it out.
The same goes for plastic and silicon food containers that have sat too long. You need to throw the whole thing out, not just scrape it into the bin. That shit is pervasive and sticks around, and plastic is a semi-porous material.
Wood, likewise, is porous. Wash your cutting boards with as hot of soapy water as you can, let dry completely, soak in distilled vinegar, let dry again, then cover in mineral oil to seal. You don't need to do this *every* time, but always at least wash with hot water. Wiping it off isn't good enough.
Your glass containers will still have some kind of porous seals. Be careful to clean these seals really, really well.
If you want to be extra EXTRA safe (and this is just good practice), you need two cutting boards: meat/fish/etc, and vegetables/fruit.
VERY HOT = sanitized. Dishwashers generally are good at getting things clean because they run at such high temperatures. If you are washing up by hand, wash from least dirtiest/goes in your mouth dishes > dirtiest utensils and pots. Glasses, silverware, plates etc need to be washed first in as hot of water as you can stand. Take your time with them, too.
Please wash your counter/bench tops. Soapy water + vinegar in a spray bottle, spray on, let sit, then wipe off.
Wash your dishwashing utensils regularly. I honestly hate sponges and much prefer dishcloths, because sponges are a bacteria's wet dream. Dishcloths you can buy a stack of and never have to buy them again, and you can chuck them in a hot wash to make sure they're clean. If you use brushes etc make sure you wash those with VERY hot water regularly.
Most food cannot last longer than a week in the fridge. When in doubt, toss it. Better to be safe than sorry.
If a container is bulging, don't TOUCH it, don't OPEN it, throw it OUT. Botulism paralyzes you!
You are playing Russian roulette with leftover rice. Genuinely it is serious. If you take anything else as seriously as you do botulism and mold, please take leftover rice seriously. There is a specific bacteria that lives on rice which does not die in the cooking process and it rapidly multiplies when the rice is warm, room temp, or even slowly in the fridge. Either take EXTREME care when cooling your rice (do not. leave it. out. in the rice cooker. PLEASE). Or just pack it FLAT when it is STEAMING HOT into a very thin tupperware or food storage bag and lay it like a book in the freezer. When you want to use it, just chuck it in the microwave. It reheats better that way anyway since all the steam got trapped. The rice is almost new, not like weird crusty fridge rice.
Don't f around with dairy either.
With the exception of like bread, and some vegetables and fruit, do not leave actual food out on your counter overnight and then eat it. I beg. People do this so much with pizza or takeout. Please just put it in the fridge, even if it's the whole box if you're not feeling up to packing it.
It is genuinely okay if you are a person that struggles with leftovers/packing food/passage of time/etc to just use frozen or pre-packed/canned/etc food. Especially if it's frozen fruits or vegetables bc these get picked right when they're best and immediately frozen. It's not lazy and it's not cheating. Please also try not to feel bad about throwing out things you're not sure of. It's better to waste food than to get horribly sick.
When defrosting meat, do not just chuck the whole thing in the fridge. Place it in a cold water bath and THEN chuck it in the fridge. The cold water helps distribute the temperatures better and it defrosts both faster and safer.
If you are a person that eats meat, get yourself a kitchen thermometer and learn what temperatures are safe for specific meats. If you do it a lot, then you CAN generally know when meat is done, but a thermometer is just extra extra safe. Test it in the thickest part of the meat, and make sure you're not putting it up against a bone for an accurate read.
When washing greens esp give them a couple passes. Best way to do this is to dunk them in a bowl of water and swish them around. Adding a little vinegar to the water also helps a lot. They do make food soaps but I find those always leave a weird taste. Even "pre-washed" greens need to be washed.
EDIT: I forgot to say, when packing your fridge/freezer, do not pack raw food on the same shelf as cooked food, and do not pack raw meat on the same shelf as ANY other food. Raw meat needs to go on its own at the very bottom of the fridge/freezer. Then other raw food on the next shelf. Cooked food goes at the very top.