The depth to which they should be inserted will, of course, vary with the plants being propagated. Remember to firmly press the rooting medium around the cuttings, and make sure you water them very thoroughly, and make sure they never dry out completely. Also, particularly during the first few days keep them out of direct sunlight. The leaves should remain firm and never be allowed to wilt. Then, as plants begin to root, gradually increase the light intensity until they are in full sunlight.
Temperature can be quite critical.
Root formation can be stimulated if bottom heat is provided. You must ensure an adequate supply of moisture. But never let the rooting medium dry out completely. At the same time do not allow it to become water logged. There should also be sufficient air circulation so that moisture does not remain on the leaves constantly or for too long a time.