Here are three tips to help you navigate those murky post-breakup, pre-officially-divorced waters:
1. When do you drop the news? Waiting until things get more serious can make it sound like you've been deliberately keeping a secret, which can put cracks in any trust that's begun to form between you and your new potential love. On the other hand, dropping the news 15 minutes into your first date with them can be really intense and awkward, as well as making a bigger deal out of it than need be. The best bet is to do it sometime during the second or third date, when you know that you actually like this person and could potentially see things going somewhere.
2. How do you tell them? The most organic way is to let them know if it comes up in conversation, i.e. if you're asked about your past relationships. There's no need to make a huge deal out of it: a simple "My ex-husband/wife and I ended things a couple years ago, and the divorce should be finalized in about six months," (or however long it's going to be), is all that's necessary. If the topic doesn't look like it's going to come up naturally, wait for a pause in the conversation, take their hands and say something like: "I like you, and I would definitely like to see if this goes somewhere. However, in the name of full disclosure, I should let you know that although I am completely single emotionally, I'm technically still married. The divorce papers are the courts right now, and should be finalized sometime in the next six months."
3. How do you make it clear things are OVER with your ex? If your new potential significant other has any misgivings about finding out you're still technically married, their insecurities will most likely come up in the days following your announcement. To prevent as much insecurity as possible, it can help immensely to give a very brief description of what happened ("The spark was gone and we decided it was better to go our separate ways," or "S/he was unfaithful, so we decided to end things,") plus an assurance that you've worked through what happened and are completely 100% ready to move forward. That way, they won't sit there, wonder what happened and fret over whether or not you're actually over it. Avoid diving fully into what happened: on only the second or third date, this is potentially TMI. But a short, sweet and non-angry description (if you're still actively and uncontrollably hurt or angry, you may have some more work to do to move completely through it) of what happened should help alleviate any fears your date may have.
Divorce and the requisite scars that the dissolution of a long-term relationship can leave behind can take a while to heal, and there's no "right way" or time-frame to move on. For some, the readiness to move forward and onward happens waaaaay before the divorce papers are finalized, and for others, it takes a little longer. Only we can tell when we're ready to find love again.