New to the salt water game.

hello,

i have just recently purchased a 120g tank, and was concidering making it into a salt water tank, as i am new and dont want to fail misseably is there anyone out there with a few tips or pointers, or even secrets their willing to part with to help me get on my way?

i aso have a 120g fresh water tank with 2, 9" tiger Oscar's, and 6 danyoh's and a plecho almost 12", that is flurishing and thriving. i also have a silver arrowana but hes only about 4" right now.