Some of this may come down to semantics: what do we mean when we say "expectations"? I think, for many people, the word conjures a check-list of demands or requirements. It also tends to include a sense that if these demands are not met, the expectation-holder will sever ties over the deficiency. This sense of expectation is a rubric to be met or a test to pass.
When I ask someone what are their expectations, I am not looking for the Cliff Notes to get an A in a class. Expectations, to me, are about what possible outcomes do you see. We have these for all parts of our lives, but in the context of potential or over romantic encounters, I am asking the other person, "What are the possible future states of relating that you see existing between us?"
The answer to that question, for me, is never a checklist or a scenario I can state off-the-cuff. It is a dynamic process of discovering yourself, including your desires and limits, and discovering another person, their desires and their limits. It's not about predicting the future or even knowing exactly what you want--but, it is, at bare minimum, an acknowledgement that we are active participants in the relationships we have and their outcomes.
I don't know how this process sounds to others, but to me it sounds like a great joy! I cherish the time spent with others who want to discover themselves, to think about their motivations and stumbling blocks. I appreciate even more the opportunity to have a dialogue with another person who wants to discover the common ground, the common possibilities when we come together in community. It is an exercise in honesty, trust and truth discovery about ourselves, the other person, our relationships and the world at large, which we come to know in new ways through our relationships with others.
Nihilism of the "no expectations" variety may come across as easy-going and care-free, but it is actually a simple denial that we are responsible parties to our futures. "No expectations" is saying "no" to considering the possible worlds we may know through and with others and "no" to our role in doing so for others.
So give me your expectations! Don't be afraid to be honest about your needs, your concerns--don't be afraid to dream of the future. Let your open-mindedness come from a willingness to grow and change, to have expectations and evolve and bring you closer to others through empathy. Leave the so-called casual experience of others behind and take the plunge: you may actually get to know someone and even a bit about yourself along the way.
* While I've framed this mostly in the realm of romantic relationships, I would posit that this is an aspect of all relationships and is something one could participate in with someone before adding a romantic element to that relationship.