My recommendations are as follows:

- Use large tubs rather than small planters (you should be ok, from what you mentioned)
- Use a well draining "container" planting mix (which is typically potting soil (sphagnum, perlite, vermiculite) mixed with bark. You can also create this yourself by mixing 50% potting soil with 50% coarse material, such as perlite, or shredded bark.
- Do not "layer" any material. Use the mix above throughout the entire container. A typical mistake is to put a layer of stones at the bottom etc. Contrary to common belief, such layering does not help drainge (it makes it too wet for lilies). Use the mix throughout the entire container.
- If not already included in the container mix, Use an all purpose 20-10-10 flowering plant fertilizer in early spring as the bulbs break ground, and repeat just as the main flower show starts.
- Since you are growing in containers, make sure you water regularily to avoid the soil drying out. Be a bit careful in the spring when the temperatures are cool and the growth is limited, but in late spring/summer be very careful about watering reguarlily. You can use a diluted soluble fertilzer 1-2 times per month (such as 15-30-15 miracle grow diluted with 1/2 tsp per gallon of water). This helps resupply nutrients which leaches easily.
- Other than that, simply leave the stems to die back naturally in fall (and remember to cut the seed pods of from the stems after flowering for added bulb strength).

Good luck