I didn't bother for ages fluff but then I started and it's a nice way to monitor stuff so I've kept at it. Only do it once a day, takes a second.
Sit on the loo, pop a clean finger up there and feel to the back, you should feel a sort of donut shape. Everyone will be different so it's about knowing how you change over the course of your cycle.
It gets higher, softer and the hole a bit more open when I'm ovulating, so the sperm can go in.
Between ov and af it gets firmer (the change is pretty minimal) and a bit lower.
During af it's low, soft and open, so the blood can come out. And when I've been pregnant it smooches right up after ovulation, sometimes I can't really feel it, and soft (if you poke the outside the donut gently, never the hole).
I check cm at the same time.