we're waiting for Indie's season too- she's coming up for 9 months though. i am no expert as haven't had an in season bitch before but i've read around quite a bit...
I've been told some bitches keep themselves impeccably clean, so you might have to wait until she hasn't 'licked' for a while and then get a piece of tissue and wipe
it's important to keep track of when they start!
also, apparently the vulva swells outwards and can get red in colour too- so locate and check!
unhelpfully, apparently any sort of behavioural change (e.g. more clingy/more independent) can be a sign of an impending season so the off her food might be indicative- but then indie goes through phases of eating like there's no tomorrow and then not being bothered and she's not showing any signs!
also! has she started 'flirting' with the boys on walks yet? or are they showing the slightest bit of increased interest? she won't stand for them at at all yet, but she might fling her backside in their direction or tease them perhaps. Again, i guess all bitches will vary! so just keep an eye out for how other dogs are reacting to her, how 'she' looks and any other changes- and keep the tissues handy if she's being clean!