Age at first heat varies considerably, but I'd say the average for Boxers is around 9-11 months. Mine have come in for the first time at 21, 17, 17, and 15 months, and they cycle about every 8 months (the latest first-season only came in every 10 months). A season can last up to 28 days, and you want to be careful throughout the whole time - some bitches can ovulate as early as 3 days, or as late as 25, so you can't just say the 'danger' time is days 8-14 and figure you're safe the rest of the time. The two litters I've had, we bred the bitch on day 11 the first litter and day 18 the second time (same bitch).
We have the panties - easier IMO to finagle than diapers or boys' undies, but then I have multiple intact bitches so use them more. We used to have the kind you put a pad it, but those weren't the greatest - the bitch would often pull the pad out, or it would slip, and the elastic straps broke, etc. So now we have the kind that have an absorbent lining with flannel, and we have three pairs - one they're wearing, one clean one waiting to be worn, and one in the wash. You don't leave panties on the bitch when she's in her crate, and if she's not crated then you need to take them off for a while throughout the day, so that she can clean herself and to discourage bacteria. We also have old quilts we throw over the couch and the bed whenever someone is in season, so that on the lighter days they can go panty-less.
Can you really not spay show prospects??? Why is that?
The point of dog shows is to evaluate breeding stock, so all exhibits must be intact.
We have noticed that Roxy has been looking a bit pink around her 'area' and seems to be cleaning herself a lot recently and so are wondering if that's a sign that she's due soon??
It could be - it could also be a sign of a slight infection, so you just want to keep an eye on it. Generally the vulva will swell, usually considerably though some females don't swell much, especially on a first season. If you're thinking she might be coming in, a white tissue pressed to the vulva after each potty trip will pick up the first sign of color.
As a side note, while spaying before the first season may decrease the chances of mammary tumors, it may also increase the chances of other cancers or health concerns. I highly recommend this article, which discusses both the risks and benefits of spay/neuter, before any decision is made.
http://www.naiaonline.org/pdfs/LongTerm ... InDogs.pdf