Both of the instances you mention are definite signs of attraction. The catch is whether or not they are consciously aware that they like you yet. I always give women the benefit of the doubt and assume they are not aware when they do very subtle things, given my past experiences. And yeah, marriage is just a piece of paper and a ring, as much as I hate to admit it.
Generally speaking, people are friends with the opposite sex because they are attracted to something, whether they are aware of it or not. But trust me, something is there, be it mutual or one sided. Don't forget, they can be both...meaning they can be your friend AND a serious, attractive possible fuck...those are usually the best kind.
The way to safely test the waters is to respond in kind...SUBTLELY. If she touches your shoulder, and some point in the convo, make it a point to touch her back, preferably the same way and place she touched you. This communicates to her subconscious that you like her as well. Eventually, if her situation is right (no external/internal reasons to not pursue you), she will make a move...or, if you get a good enough read, offer her your number and tell her that you would love to hear from her sometimes.
) besides what you told Inrgee he should do (make it a point to touch her back..)