@Riverlee The quietest times are normally early morning and after 4pm. Leading up to 4pm there will be a lot of exhibitors and their dogs moving from the halls to the dog exits in each hall, as that is the earliest those exhibiting can leave. If you were showing at 0830 or 0900 and did not win Best of Breed it is a long wait until 4pm to get out so there is always a rush towards the exits.
Head to the YKC ring, which is normally in hall 3, they have showing, obedience, agility and various other things going on all day. It is a lot smaller than the main arean and the flyball/obedience areas but it will give you a taster of various canine events. There is always a lot of space around that area so if you need to sit down it is a good place to do so.
As others have said it is a long way from halls 1 to 5 so cutting through the NEC concourse (where there are also food outlets and toilets) is a good idea. When in the concourse you can always go outside from some fresh air if need be.
Hall 4 is always very cold, other areas not so much, but does depend on the outside weather.
Other than asking if you can say hello to the dogs, even on the Discover Dogs stands, the biggest piece of advice is watch when you are walking as you will share the same space as exhibitors walking there dogs into, out of and through the halls - it is always amazing how many people go to Crufts and get annoyed they may have to move out of the way for a dog coming through! Also watch for treading on paws in the really busy areas.
Hall 5 normally has a large screen where you can watch events live going on in the main arena, there are always tables and chairs there so it is a good place to rest, have a cup of coffee and watch the screen. When leaving there do not forget to collect your shopping bags, as we all say we will never buy anything!
I always have to buy something that my dogs manage to grab from the shopping stands as we walk by!
For those going for the first time, it is a magical experience from the moment you arrive on site, even before getting into the halls, you will never see so many dogs, or so many breeds all in one place from the car parks, the railway station and then into the halls.
I am there 3 out of the 4 days this year, showing on one day and covering Discover Dogs for 2 days, very tiring but always enjoyable.