I think the BIGGEST mistake that can be made on a first date is to screw up the communication. Obviously when you are going on a first date with someone new, you want to get to know him/her and vice versa, so communication is the most important and is what will really count. I think two of the worst things you can do on a first date is to make it an interview or to turn it into an autobiography. And I will honestly say that we women are just as straight-up guilty as men on this one; no bias there.
DON'T MAKE IT AN INTERVIEW
Many people assume that asking a lot of questions on the first date is a good thing because they think it's the best and quickest way to learn the most about the partner. In reality this isn't even true because:
1) You'll learn a lot more about someone, especially their personality, by being around them and,
2) People do lie, sometimes without even realizing it, in order to get the best outcome they can.
I cannot stand to be asked several questions straight in a row... unless, of course, I'm in an interview. This will actually make me lose interest in a guy really fast. Be mindful also of the questions you choose to ask your partner on the date. Asking about his/her career is an example of a good question that probably should be asked, mainly because most of the time you won't learn the answer just by spending time with them.
However, questions more related to personality are pointless, at least in my opinion. It's pointless to ask someone if they are religious because if you get to know them and they are always in church and they pray daily then what does that tell you? Or asking something like if they are usually honest and truthful... well, if you get to know them and almost everything they have told you can now be proved wrong, then again that question is pointless. Instead of asking so many questions, have a real conversation. Questions are not the center for conversations. If you need to, go out and work on your charisma.
DON'T TURN IT INTO AN AUTOBIOGRAPHY
Honestly, sometimes it can sound a little egotistical if someone is talking about nothing else except themselves. Even when you know the person as a very meek and kind individual, you're still not there to listen to a life story. Yeah, I'd like to know some interesting things about you, but don't tell me something about your life every time I say something. It does get a little annoying.
KEEP IT A DATE
Have real conversations, share a little charisma, and even enjoy the quiet moments. There are times when talking isn't even needed. A good topic as an example is common interests - and this does not mean asking a lot of questions about interests until you find one. It means if you do happen to come to one within the conversation, build on it without asking a million questions and without telling just your experience and what you think of it.
Meeting and getting to know someone new doesn't have to be a lot of annoying questions or stories about yourself. Make it various and make it fun. Have a little charisma. :)