I started out using the "closed" reed calls for the 1st 10 yrs, then I went to using the "open" reed calls. I then stayed with this type of call for the next 25 yrs.
My favorite call has been the "Pee Wee" open reed call, I can make a lot of different notes with this little jewel. Open reed calls are really the best to use - no freeze up in the winter months.
Learning the habits of the animal that you want to hunt, is important in being successful in taking the animal. Learning where the coyote lives, where he travels to day and night, etc. I would have to say that probably 65% of the coyotes that I have taken was from stocking them.
Here is link to the ones that I use, but there are lots of call manufactures that make these type calls, so don't be afraid to try several different brands. Open reed call