Whoa there big felle.....you need to read those stickies on top of the page....
It seem as if you need to do a ton of research, I am not trying to be a dick but just trying to save you from doing something that can do some damage on your body. What does your training and diet look like right now? how many calories/protein are you getting in on a daily basis.
First off, deca only cycle.........NOPE!
Second of all, decide on what your goals are, cutting/bulking.
Third thing, READ, READ, READ! This is a great board to learn from.
Last but not least........READ!!!!!