I would like to add a bit about Opium due to the large amount of Opium related threads that have been popping up in OD and BDD.
It is important to first recognize what you have, i.e. if it is actually Opium. Erowid has a neat page about the "Red Rock Opium" (incense sold as Opium) hoax; and descriptions given by BL posters about the texture, packaging, etc leads me to believe a lot of people are simply selling Heroin as Opium for a higher profit margin to people who are opiate naive.
If it comes in a glassine bag with a stamp on it, it is Heroin. If it comes in a balloon or wrapped in foil, and is a moist looking black color, it is most likely Black Tar Heroin (this is important to remember if you are on the West Coast/MidWest).
Real Opium goes through a few changes depending on its state. After slicing the seedpod open, the Opium latex that flows out is white or off white. After it dries it is a light to dark brown, Opium gum. While it is possible to do so, it is better to treat the Opium to make it more suitable for Chasing or Smoking.
Here is a guide from the famous Federal Heroin guide:
http://www.shaps.hawaii.edu/drugs/dea20026/dea20026.html#cooking
(
Note: the article says to use 'boiling' water; do not do this. Hot water, not
boiling. Never add opioids to boiling water, or boil an Opioid solution.)
After this is done, Opium can be Chased or (if you want to waste it) smoked like Heroin, Morphine, or other opioids as outlined in the first post.
Since Opium gum is most likely not cut, it isn't necessary to worry about diluents that reduce volatilization. However, it would be a good idea to add a cut that will facilitate volatilization as explained in the first post.