Safety is always priority #1 for us when designing outdoor landscape lighting systems.  Steps leading from a deck to a yard can be some of the most dangerous areas to negotiate in the dark, especially if you are a guest and not as familiar with the property.  Some deck companies will sell lighting packages with the deck to make a few extra bucks while they are installing it, however what I have generally seen is tiny lights sitting face up in the deck steps themselves which causes 2 issues.  

First, they don’t illuminate the tread you are needing to see because they are pointing straight up and second, because they are pointing straight up, they are putting light in your eyes at the worst possible time when you are trying to negotiate in the dark. 

This is the worst possible way to “light steps”.  The most effective way to promote safety in these areas is to mount lights from above and illuminate down on the treads, either from an adjacent railing post or lights mounted directly above the stairs.