l am looking for a stud dog for my tri-colour bitch cavalier king charles  just ready for first season would like to find a mate for later in the year. 

As Cavaliers have quite a lot of heart problems you should have yoiur bitch heart scored by a specialist Cardiologicst.  The same of course applies to the stud dog, and you sdhould also make sure that both your bitches parents were still heart clear at above five years of age, ditto for the sire.

For this reason alone it is important to have knowledge of the ancestors of your bitch and the proposed sire.

If your bitches breeder was reputable and experienced they should be able to advise.  You should also join one of the breed clubs, and also your bitch should be at least 2 years old before being bred from, and have other breed specific health tests, Hips Scored and eyes tested I would imagine.

An experienced breder will be able to advise if your bitch is of sufficeint quality to be bred from.