I see a stickied thread for Cading Tips but not one for inexperienced zambies so I'd thought I'd start one.
A few tips right off the bat;
1) If you're not a deformed and are stuck in a cade, ztele or do whatever you need to do in order to get out. At best you're providing free points to whoever is cading as they shoot you and at worst you're blocking your teammates from attacking the cade.
2) It isn't always about you and your rank. Teamwork can apply just as much for zombies as it does humans. Don't be afraid to assist in breaking a cade apart knowing that you won't be able to get the tags.
3) Mess stuff up from below. If a caded room has an area beneath it, chances are that jumping up and holding onto E will flip around the fun stuff they have in the room above, which at very least will require additional time and ammo expenditure to repair, if not breaking it apart entirely to allow your teammates to grow in number.
4) #3 applies for walls and sometimes for roofs as well, if the latter is low enough, such as some red shipping containers.
5) Have a tough time breaking a bookcase apart? Crouch and let a teammate stand on your head. Various methods can be used in that instance to pull bookcases apart. The more zombies working on it, the more fun stuff that can happen to a bookcase cade.
6) On escape maps, if you see a zombie running on the left side of a passage and they're being shot at, run to the right side or in the middle. Make the humans divide their fire and be less effective.
7) Diversify in zombie type. If you see a lot of zombies being one type, try being another type to mix it up a little bit and present a tougher challenge for the humans. Unexpected challenges can reap great rewards, whether it being a deformed in a pack of normal sized zombies or a fast zombie running rings around a pack of slow deformeds.