This category is certainly the easiest and least demanding, so why do so many people kill them?? The most common cause of succulent death in captivity is being "loved" to death. It's hard to resist watering even when it isn't needed. Root rot due to overwatering and/or incorrect soil that holds too much moisture are the leaders in succ murder.
These plants are native to deserts where the direct sun is relentless. They stand for months on end with nature having zero f*!ks to give about providing water. Yet they grow and thrive in these harsh conditions. Here's how it works. The soil is sandy, rocky, and when water does happen it is often in the form of a sudden down pour after long spans with no water. When this happens the roots take up the water while it is there because as quickly as it arrived it will be gone with the sun's heat. This water is taken into the leaves and/or stems and it's gonna be there awhile. During the day's heat the pores of a succulent remain tightly closed to prevent the moisture inside from escaping. At night with the temperature drops and darkness sets in the pores open to allow respiration and for the plant to take up any moisture that might hanging in the night air.
HOW TO NOT KILL YOUR SUCCS:
First, have them planted in well-draining soil that retains little to no moisture. A good general mix is 3 parts potting soil, 2 parts coarse sand (turface or poultry grit), and 1 part perlite (or pumice). The perlite or pumice give good aeration so that when the watering occurs it can flow around the roots. Check out this mix shown in the palm of a hand.
And this one that I made myself with what I had on hand (perlite, orchid bark, and organic potting soil).
Oh the watering, where so often we go wrong. A good rule of thumb-if you think the soil is dry enough for a watering wait 2 more days anyway. When you do water direct the water to the soil (underneath of the plant to avoid pooling water on any leaves or in nooks and crannies where it can cause rot, fungus, and mold). Allow the water to run through the soil until is running steadily out of the drainage holes. Then WAIT. WAIT. WAIT until the soil is 100% dried out before water again. Honestly, forgetting about the water for a while isn't a bad idea.
Your two best friends when watering succs and cacti are lab wash bottles and saucers. The lab wash bottle has a skinny spout and dispenses water from the bottom of the bottle. This makes it easy to squirt the water under succ leaves and directly into the soil. The saucer is great for bottom watering/wick watering. Put about 1/2 inch of water in the saucer and set your succulent in for 15-30 minutes (longer for the bigger pots like 8 inch plus). We have lab wash bottles available for $3. Here are my tools.
Your succulent will let you know if it truly is thirsty by beginning to wrinkle or shrivel. If you see these signs it is DEFINITELY safe to water. If your succulent starts getting droopy leaves, yellowing leaves,or mushy parts you've over watered. It can be very difficult to save at this point which is why it is always better to skip more waterings than to overwater. If you see early s of this get your succ out of the soil, remove and parts of the roots that are mushy or smelly, allow the roots to dry some before repotting in a good succ soil and, with luck, you might save it. If the roots are all rotten and/or the main stem is mushy or black it's probably a lost cause. Alternatively if there any good cuttings left on a rotting succ your best bet may be to take those and propagate. This one has
some leaves near the very top that could be salvaged and used to attempt propagation. Note the discolored mushy appearance of the lower leaves. The color of the lower leaves tells me that root rot is likely to have set in beyond saving the existing stem/stalk.
Most desert succulents and cacti thrive in direct sun and sun stress is often how they get beautiful color changes (like the red in firesticks or bronze on aloe). The beautiful red color at the top is achieved only with direct natural sun. The entire plant will be green like the bottom portion if there is not sun stress.
Always educate yourself on this because there are succs that grow under shadow of taller plants, for example, String of Pearls. With all of your succulents, if they've been kept indoors for winter, you'll need to slowly expose for short periods of time to direct light when moving them back outside. Going from inside to outside into full direct light all day will cause sunburn. I got eager last spring and moved my plants outside on an overcast day. The next day was clear skies and direct sun and BOOM cue sunburnt plants. All of my sunburnt plants survived, luckily. My starfish snake plant is scarred for life. 
Humidity needs are pretty straightforward: DRY af to normal household humidity. Never mist your succs. The moisture can get trapped in the crevices and cause mold and rot.
Fertilizer? When you think about the conditions they survive in their natural habitat you might think these cuties don't need fertilized, but you'd be wrong. When they get the big rush of rain they are also getting a tea of sorts from the all of the dead and shed pieces of other plants. So once a year it's a great idea to give your succs a drink of manure tea. Alternatively, you can use epsom salts at a ratio of 1 tablespoon to a gallon of water. Sometimes the best and easiest route is to buy succulent/cacti fertilizer that is pre-mixed and follow the directions. A big important rule here is that if you are using any fertilizer or fertilizer recipe that isn't specifically for succulents you should dilute by half.
A common ailment for succulents and cacti is fungal infection. Fungal infection can be sneaky. It often shows up as a slow growing brown spot. Initially this spot won't feel mushy or wet, but allowed to continue it will eventually begin to rot the area it grows on. And it is contagious! Spores are invisible to the naked eye and easily transferred from one plant to the next, especially through touching. If you've touched a spot that is suspected to have a fungal infection wash your hands thoroughly with warm soapy water before handling other plants. To treat and prevent fungal infections there are a variety of products out there including organic natural copper treatments. These can take awhile to get knocked down so be prepared to keep on the schedule recommended on the product you use. Check out this fungal infection on the cactus below. This is currently being treated with Bionide Copper Fungicide. In the store we use cinnamon as a preventative and treatment for mold and fungus.
The last topic for succulent care is about pests. I generally see aphids or mealy bugs on succulents. Aphids especially like when succs grow a stalk to bloom. Mealy bugs love to settle in for the long haul under the leaves and in those nooks and crannies. For both I recommend using alcohol on cotton swabs to remove the pest manually. I don't like to spray neem oil on succs since it can clog the pores, but I will spray it on the soil around the plants. You may have to remove the pests multiple times over the course of a few weeks. If you're plant wasn't already damaged too bad by their presence it may be saved. If you have pests the affected plant should be quarantined away from other plants. Here are the disgusting ass mealy bugs on a succulent.
I've shared a great deal of info here and I hope it's helpful. If you have questions we always welcome them! Reach out via the contact form on this site, via Insta or Facebook, or via email theplantcult@gmail.com.