Trading Guide
First lets start with what rarities there are:
OMG So Common (OMGSC) -> Very Common (VC) -> Common (C) -> Uncommon (UC) -> Rare (R) -> Very Rare (VR) -> OMG So Rare! (OMGSR) and also unknown
OMG So Common (OMGSC) -> Very Common (VC) -> Common (C) -> Uncommon (UC) -> Rare (R) -> Very Rare (VR) -> OMG So Rare! (OMGSR) and also unknown
Demand
Every pet has a different demand, date and rarity. Lets talk about demand. Some pets will be Very Rare from, lets say 2009, but it will be low in demand. When trading demand is one of the most important things to think about when editing, or suggesting a trade. The more people who want something, the more popular it is. The more popular it is, the harder it is to trade for. Demand must be taken into account with all pets, even certain commons are more in demand than others. For example here is pretty fair trade as an example, Click MeThat trade is pretty fair because, the pickle has a higher demand the pineapple even though the pineapples face worth is more than the pickle. This trade is fair to some people not all people
Date
Everyone hears talk about the dates of pets. Dates MATTER, a lot. A very rare from 2008 is MUCH more rare then a very rare from 2011, to make the trade fair for something like that check this out as an example, Click meThis trade is some what fair because the 2008 very rare is pretty high in demand and the date makes it worth even mo0re, so the trader traded a 2013 very rare along with other things that make the trade fair. For an example of what not to do click these,Click me and Click me.
Rarity
For Rarity all pets will have a rarity tag like:

These tags have different meanings, OMGSR being the best, VR being second, Rare and so on. Sometimes things that are higher in demand and are from a later date are worth more than OMGSR's. You have to look at each factor and see how the person trades and what they want for the specific pet, some people like Rare for rare or VR for Vr unless the demand and date make it worth more then it could be what is known as a BULK trade which is a large trade of things with different rarities. Such as; Click Me

These tags have different meanings, OMGSR being the best, VR being second, Rare and so on. Sometimes things that are higher in demand and are from a later date are worth more than OMGSR's. You have to look at each factor and see how the person trades and what they want for the specific pet, some people like Rare for rare or VR for Vr unless the demand and date make it worth more then it could be what is known as a BULK trade which is a large trade of things with different rarities. Such as; Click Me
Conclusion
So in conclusion, rarities are truly complex and are not easy to grasp. This guide only touches the surface on them. Just keep in mind that not all rares and very rares can be interswapped, and make use of your resources around you. Please PM me, or post here with any questions, and I would be more than happy to answer them.
As well, please post here with any subsequent information I am missing or should cover. If I made any spelling/grammar mistakes, please let me know. If this is completely stupid and I shouldn't have made it, lock it. c: