tips for succesful propagation
1.LEAF
Every leaf have to support the succulent pup that it will produce. the nutrients on that leaf will be sucked up by the new pup.In order to ensure successful propagation always choose the healthy and plump leaves and avoid the yellow and wrinkly ones.
2.SOIL
water and air propagation is possible but if you choose to propagate on soil be sure to use the right soilmix. 
i personaly recomend that you use any of this: cocopeat, rice hull,compost,loam soil (or you mix them together.) this are light weight soil ideal for propagation it makes easier for the roots to stablish its way down the soil. soilmix with pumice or any rocks may  be possible but expect that some of the leaves will turn black before it has the  chance to produce pups. also rocks can block the roots from digging its way down giving the pup a lower chances to survive.
avoid using pure rocks as a soilmix for propagation
3.WATER.
newly plucked leaves should be airdryed for a day before putting it in soil after that wait for another 2 days  to ensure that the leaves are caloused. if you water them early they  may absorb much water because of their open wound from where you plucked them they then will turn transparent and will eventualy die.
after airdrying for atleast 4 days you may mist them with water every other day.
4.LIGHT EXPOSURE
   place your propagations into  a bright bright shade. as they grow begin to introduce them into the sun.Provide atleast 2 to 3 hours of morning sun.

some succulents produce pups within one week but  some may take  2 to 3  weeks  before producing one. 
NOTES:
1.ALWAYS remove the  dead leaves from the    propagation trey
2. do not let your propagations dry out for a long period of time   remember to keep it moist. succulent propagations  commonly has   young fleshy leaves that are prone  to insects such  as  aphids .  keeping it  moist  will help to  keep the  bugs away.
3.dont bury the leaves too deep  why? because  the leaves may form roots but will not produce pups. just place them on top of the soil they'll be okay
4.transfer them when they're an inch bigger to ensure higher rates of survival if you'll transfer to another pot  too early   you'll disturb the growth of the plant.

Leaf propagation may take  time thus PATIENCE is must🤣🤣😁