Not an experienced mama, but a pretty experienced charter--I too am charting but not quite ready to TTC.
Just to give you an idea of my journey (I am on chart/cycle #8). (Note:haven't been on any type of chemical BC in last 4 years, though, but you likely will have an 'adjustment period')
My first chart I was super excited on day 14 when my temp went up and I had classic CM signals for O. Then 2 days later my temp dropped back into follicular phase range and stayed there and CM went crazy (wet-dry-wet-dry).
#2 I O'd on day 24 of a 28 day cycle
#3 I O'd on day 27 of a 34 day cycle
#4 I don't believe I O'd at all, but at best I O'd on 19 of 26 with lots of dropping under coverline
**During cycle 4 I started taking chasteberry, 50 mg zinc, cod liver oil, and got really serious about darkening my room at night (resource:Katie Singer, Garden of Fertility)
#5 I O'd 19 of 31, luteal phase temps all well above my coverline (Exactly 12 day LP!!!!) CM perfectly matched up!!! (We celebrated!
#6 O'd on 18 of 30 (temps stayed way up for 12 days, CM right on)!!
#7 O'd on 15 of 29 (temps high and 13 day LP)!!
I guess what I am trying to say is that if your charts look pretty bad at first, educate yourself and make changes and definitely don't let it freak you out!!
As far as AF warning, luteal phases tend to be more predictable than cycle length, so if your LP is 12 days one month it will likely be about that next month (helps predict). Also, as already mentioned, your temp will drop pretty noticably on the day AF starts. I notice I can even predict time of day it will start based on how drastic the temp drop is (big drop=morning, not so big drop=evening--that is just my experience--not scientific!)
Hope this helps!