What are the most effective ways of dealing with and reducing stress?

There are many ways in which you can deal with stress and potentially reduce it. 
You can try meditation - this kind of relaxation is known to help a person deal with this kind of a problem. Meditation may alter the brain's neural pathways, which in turn makes you more resilient to stress.
You can take deep breaths - if you focus on breathing properly, you won't give stress time to come and bug you. 
You can try exercising - yoga is especially good for people who are stressed.
Eat better and healthier food - although this may seem irrelevant for dealing with stress, it really isn't - try it!
Start reading a book - this kind of escapism makes you feel better and reduce stress faster.

Hope this helps! :)