1. These are my recomendations, not rules
2. Plant in ground after last frost in your area or plant in pot anytime.
3. Dig an area a foot or two around where you plan on planting.  This allows the plant to spread roots faster.  Loosen the soil below your tuber also.  A few inches should be good.
4. Plant tuber around 2" below surface.
5. For plants that are not dormant you may plant up to the point on the plant where the trunk stops and new part of plant begins.
6. Soil should be prepared with compost mixed in.  Topsoil from your local Lowes or Home Depot is also good to mix in.
7. Water plant/tuber in pretty good at time of planting.  Once you see the plant start to grow (which could take up to a month or two, some times longer) you may increase your watering.

Colocasias enjoy a moist soil and like to sit in water.  I only advise others to place in water during growing season.  Some do fine in the water when they are dormant but other will rot into nothing.

Light Requirements

This is were it can get tricky.  Depends a lot of variables.  One, it depends on where you live.  A summer day in West Palm is much more intense then one say in Kansas City. 

Most Colocasias can take full Sun but don't mind a little bit of afternoon shade.  Some can take full shade but tend to grow very slow.