There's one thing all daters (over the legal drinking age) can probably assume about their dates - they've been on dates before, with other people.
We all have. And most us have had prior relationships.
Remember, and this is very important (note the bold and italics), those prior relationships are in the past. Your date's prior relationships and YOUR prior relationships are all in the past.
It can be incredibly helpful to imagine each first date as a clean slate. Sure, you have ex-boyfriend/girlfriends. In some cases maybe even ex-wives/husbands. But those relationships are over. And it's rarely helpful to mention them on a first date. It can, in fact, be quite harmful.
Instead, focus on the present and the future. Talk about the positive things that are happening in your life. The things that make you happy. Share your joy. And, more importantly, dream aloud about what you'd like to see happen in the future.
Save discussions of the past for if and when you get to know your date better. Until then, imagine that you have a clean slate: no exes, no break-ups, no past relationships weighing you down.