Etiquette of Reaching out to a 2nd Degree Connection?

I'm confused what's the etiquette of reaching out to a 2nd degree connection. I hear people often say, "if you have someone in mind, I'm happy to introduce you," but I always find it easier to message them directly and ask how he/she knows of our mutual connection. If you don't know who to talk to, then I understand an introduction is more appropriate. 

I recently did this and the VP  got back to me on the same day and expressed his willingness to speak with me later in the week. I was trying to schedule a time with him but just never heard back and it has since passed. 

I am wondering do people contact your shared connection to get an initial review? I haven't done anything that would leave a bad impression but relationships are so fickle so I never know what people think of me.