What do you need to know. First you need to kow the standards that are set for every rat and then the standards that are set for the classification of the rat, which would be berkshire and the color, if she is dumbo etc. Most often Berks are shown together in a class. You first need to make sure that she is really a berk and not a banded. Berks have a white tummy that DOES NOT extend up the sides. Banded rats are similar to berkshires and have a very thick hood that stops right before the tummy, with white extending up the sides.

Every rat needs to be bathed before show, have it's nails clipped, be free of mites/lice etc.

Rats are compared NOT to other rats but what a perfect rat would be. The tail should be square at the base and not rounded, eyes need to be not poppy and of equal size, tail should not have any kinks, all toes should be there, nails clipped, no tears in ears, no sneezing. Since you just had a sickness in your colony I would wait to show your rat. Also it is manadatory that all rats entered in shows be quarantined for a minimum of three weeks. This means no new rats for about a month, no taking your rats out of the house, no touching other rats and then touching your without washing your hands etc.