You need to call around and do some research for the right pet insurance. Some key things:
1) All pet insurance is reimbursement only which means you pay for everything out of pocket and then they send you the check once you file the claim. Your vet clinic does nothing but sign the claim form.
2) Most insurance companies will not cover any type of pre-existing condition no matter how long ago it occurred.
3) There are policies for everything. Emergency only, Wellness only, Both
4) Most coverage of some items is based on the lowest average for your area (this is what I've determinied) For instance - if you want to run bloodwork and A clinic charges $50 and your clinic B charges $75 - they will reimburse the $50 because it is lower.
There are definitely good and bad companies but you need to call around and do some research. Typically it is best to go with coverage that offers a percentage rather than an amount - like 80% of the cost versus set amount that way you could potentially get more coverage. If you are concious enough to set aside money for routine vaccines and wellness stuff then go for accident/illness coverage because that is usually where you are going to spend the most money if your pet is sick. If your pet has a lot of breed predispositions or pre-existing conditions then insurance wont cover nearly as much as you need it too.
As far as premium costs for pet insurance - there are very wide variances between companies and coverages.
I have experience with some good and bad companies. PetsBest and TruPanion are some good ones. VPI isnt bad but their coverage has changed recently and I've heard that it is more difficult to get a claim filed. I encourage you to do the research and look into it.