I'm a lee-leaning switch, and I'm so ticklish that the first makeout session almost always results in my partner accidentally tickling me. She'll apologize and I'll say it's OK and I enjoyed it. Usually she'll tickle me a little more after that because everyone has an inner ler once they accidentally tickle someone who says they don't mind. Then I'll tickle her right back and see how she reacts. Some giggle, some scream, some have no reaction. But I'm so ticklish that they all keep accidentally tickling me and they keep finding my ticklishness amusing. Once the trend has been established after a few dates, I'll confess that being tickled turns me on. Most girls I've confessed to quickly begin enjoying tickling me silly and don't think much of it at all.
that's harder is finding your way if you're mainly a ler. Accidental tickling happens all the time in foreplay, and that's an opportunity to start asking questions. Some people have been so traumatized that any tickling is unacceptable. A lot of the time, a woman will confess after the first accidental tickle that she has trauma related to tickling and you know to lay off. As your relationship develops and mutual trust builds, she may come to trust you enough to allow a little tickle play. It may build up to the point where she'll really let you make her scream.
If you get an early strongly negative reaction from your partner being tickled, ask about why it's such a big deal. Have a conversation about it. Share some of your own tickle trauma history (if you're ticklish, you've certainly had a moment where it went too far). How much of your kink you want to share is a play by ear game.
TLDR: Every partner is different when it comes to tickling and accidental tickles are an opportunity to start a casual conversation about the topic and establish boundaries. As trust builds, those boundaries will gradually expand.