You’ll know that she’s climaxing when her muscles start contracting. Her vaginal fluids can increase as well, and she may become louder. If you’re having a hard time telling when that is though, you can just ask her to tell you when she’s close, about to finish, finishing, etc.
Squirting isn’t something everyone can do and sometimes it takes practice, so just be aware of that. It’s most commonly done by stimulation of the G-spot, which is an area in the vagina about 1-2 inches in on the upper wall (the wall closest to her stomach). It can be stimulated by inserting a finger or two, palm up, gently rubbing it in a “come here” motion. The G-spot may feel like a rougher patch of skin in the vagina.
Incorporating this during oral sex is a great idea, but it might take some practice for you to be able to focus on everything you’re doing at once.
If you need more tips, make sure to check out my “FAQ” and “How-To” pages. If you don’t find what you need there, send me an ask!
Hope this helped! :)