I have a bed of Easter lilies that are very thick. The ideal time to divide and transplant is in the fall after the foliage has yellowed. Transplant to a freshly worked bed of well-draining, organically enriched soil.
Lilies prefer soil that is neutral to slightly acidic.
Place a little fertilizer in each hole, top with a small mound of sand, then set the bulb. Do not let the roots dry during the transplanting process. Mulch the bed. Last year I bought a Mrs. R.M. Finch to put into my newly established rose garden. I thought it would look pretty with the Katy Road Pink, as the Mrs. Finch had white blooms.