I didn't own salt water, but freshwater and you basically have to do the same thing.
We got everything imagineable out there to help, and even kept a log for 24-48 hours. When we thought things were good, we introduced the fish and less then a week later, they had all died. (Yet everything according to our tester strip was fine)
We later found out the place we had gotten our fish from were known for having sick fish. We never got back into it, but plan to one day.
I would go around to all the fish stores and even see their reviews online before you actually commit yourself to fish from there, and also ask them a million questions about every little thing (see which ones are knowledgeable, based off of what you read online, and which ones are just pulling it out of thin air) And I would also go look at their fish a for a few weeks to see how healthy/active they are.