There is a school of thought out there that you should immediately try to get to develop a relationship with the person who can sign the big checks. The person who can bankroll the biggest of projects.
I try to do that, but it is not always possible. Not only that but it is also a sure-fire way to offend the person who helped you gain entry into the organization. If you don't enter at a high enough level, then you need to work your way up to it.
Do not fall into the trap of believing your story is so great that they will, of course, be happy to introduce you. They often won't, and they will resent you asking.
My approach? Give people something they can say yes to, and use each engagement as a means of marketing your way to the top of the tree.
If they can authorize, say, $25,000 - then that is the size of engagements(s) that you are aiming for. If they can authorize up to $250,000 then you have more room to play with.
Talk to them about what they can say yes to, not about what they can only say no to. Deliver outstanding value, make sure they (the client) acknowledge it, and make sure it gets spoken about beyond the immediate level where you have engaged.
Work into a position where you are paid to deliver eye catching results, and then capitalize on that. Bite and hold; then bite again.