I know, as you start wedding planning, every other person has advice. (Get used to it.) But this isn't something I was told or read, and it would have saved me some stress, plus a couple of unpleasant disagreements.
Don't assume that your fiance couldn't care less about the details. It's a stereotype that the men don't care about anything except for the food. Like most stereotypes, it has some truth to it, but be careful about painting with too broad a brush.
What I wish someone had told me is, "Before you do any wedding planning, sit down with your fiance and discuss anything you both have in mind." My husband surprised me with the things he actually did care about. (Yes, good food was on the list while flowers were not. I did say the stereotype has some truth.) Often I cared more than he did, and he let me have what I wanted, because that's the kind of man I married.
Example: I announced early on that I thought royal purple should be our color. Later it turned out his first choice would've been forest green. Now, I wouldn't go with forest green, and we might well have ended up with royal purple anyway, but the point is that we didn't have the conversation. I steamrolled through and assumed that he didn't care. Later this kind of thing led to some tense evenings.
I did learn from this a few months in, and started asking for his input. We found ways to work in aspects that reflected what he wanted. (More unsolicited advice: groom's cake. Our cake baker made a groom's cake for a very reasonable price. We ate it at the rehearsal dinner, and it allowed us to work in his love of Batman without having a Batman cake at the actual reception.)
I now see it this way: wedding planning is an excellent chance to practice communication and compromise, two skills which couples need for a good marriage.