Dq's are easy to spot right off the bat, your basic missing toes, foreign colour (like a blue spot on a black, or a white spot on a solid coloured animal that isn't white to begin with). Toenails once you can see colour in them you can tell.
Teeth on the other hand can be hard, usually by 10 weeks (the age most start showing rabbits) it's pretty evident whether they have good teeth or not. Although a rabbit that is kept too long with it's mother and is still nursing, you will often find will have butting teeth, they grow out of it within a week or two of being weaned. Then if you have a breed with a blocky head like Netherlands, because their head does change a lot a rabbit with bad teeth as a jr can have perfect teeth as a sr and vice versa.
Faults on the other hand are harder and they're what make a break a show rabbit. If you're selling a young Jr, it is really hard especially if you go over them when their in there uglies. Before the uglies is the best age to gauge your Juniors as potential keepers and what not, you'll find that faults hardly fill out they just get bigger with the rabbit. Then after the uglies you'll know for sure what is what. Just never ever ever get rid of a rabbit that was nice before the uglies but gets so ugly you can't bear to look at it (they tend to be the winners :lol: )
In most policies you'll see "Show quality rabbits are free from disqualifications at the time of purchase" mainly because things do change and it's nothing the breeder can really do about it, so you shouldn't feel bad if 6 months after you sell a rabbit it suddenly has bad teeth, you could not have known that would happen.
You should always encourage your buyers to go over the rabbits themselves before deciding whether they want it or not. As a lot of people have a different translation of "Show Quality"