1. Use a pipe or bong, no blunts or joints.
--joints and blunts give off much more smoke then pipes and bongs, so be sure to use a pipe or bong when trying to smoke without the smell.
2. Cover the bowl with a quarter right after hitting it.
--If you light a bowl and don't cover it, it will often let off smoke which of course adds to the smell. Be sure to cover your bowl with a quarter, lighter etc. quickly after hitting it when trying to smoke without the smell.
3. Smoke outside
--pretty self explanatory, smoking outside allows the smoke to dissipate in all the surrounding air and is perfect when trying to smoke without the smell.
4. Smoke by a window
--second best to smoking outside, smoke by a window and blow all the smoke you inhale outside. Be sure to close the window after because an open window in the middle of winter could be a dead give away that someone was trying to smoke without the smell.
5. Turn on the shower.
--Smoking in the bathroom with a shower on can help reduce the smell. The steam released by the hot water from the shower absorbs most of the smell and is very helpful when trying to smoke without the smell.
6. Use a sploof.
--Using a sploof (toilet paper roll stuffed with dryer sheets) greatly reduces the smell of weed when trying to smoke without the smell.
7. Don't forget a towel!
--If smoking inside be sure to close all the doors in the room your smoking in and cover the bottoms of the doors with a towel. If a towel is not available clothes or a small animal can be substituted when it is necessary to smoke without the smell.
--Use a fan to blow the smoke where it needs to go (out the window possibly?) when you are trying to smoke without the smell.
9. Spray some shit
--I personally use ozium which works pretty well but anything is better then nothing, spray something to cover up and/or eliminate the smell of pot when attempting to smoke without the smell.
10. Use a vaporizer
--Probably the easiest way to smoke without the smell, if you can get your hands on a vaporizer then it should be really easy to smoke without the smell.
11. Cook with your weed
--While I'm not sure if smell is released while you are cooking (use extreme caution :-P) once you have the finished product (example: brownie) then you can consume it anywhere without any smell at all (even school). While technically this is not smoking without the smell, it is a good way to get high without any odor.
12. Change your clothes
--If you smoke weed and then go somewhere where you don't want others to know your high be sure to change your clothes and if possible take a shower.
Remember to use all of these tips in conjunction with one another and if you are smart about it, it is surprisingly easy to smoke without the smell!