Exactly what i would typefjh said:MTS give live birth so there are no eggs. You want to make sure theres enough substrate for them to burrow (they prefer sand). Also supply lots of food - over feed your tank so your snails get some to eat, and driftwood provides something for them to graze on.
Similar for the ramshorns - provide extra food, nooks and crannies to hide in, etc.
Also if you have a puffer or loaches they may be eating the snails. In which case raising some in a separate tank will definitely increase breeding/survival rate