Training

Question
I have an 18 mos old rat terrier.  He's been with me for about 8 mos. I see to it that he's exercised and well taken care of.  He minds most of the time.  The biggest problem is that he will not come when I call him.  If there is a squirrel or something to chase, he is gone until he wants to come back. I've always read that you shouldn't yell at them when they do come back so I don't know what to do.

Answer
Hello,
 I get this question all the time.  First you have to see the breed of dog you are dealing with.  Its a Rat Terrier...They were bred to kill small vermin.  So he will chase.  You need to harness some of that drive and take him to an earthdog test.  AWTA is American Working Terrier.  You can find them on -line.
 To get to your question....Yes you are correct, don't yell at him when e comes to you.  If you scold him everytime he does come back he will continue to blow you off for fear of being yelled at. Play reward games in house or enclosed yard.  Have some high value treats.  Could be hotdogs cut in small pieces or cheese.  Call him to you and when he comes to you reward with praise and treat him ASAP.  Keep doing this till he has a great recall.  As he progresses don't treat him all the time, only verbal praise.  That it will keep him guessing if he will get a treat or not.
 Then when you feel comfortable enough then try it out in a safe environment.  You could also put a long lead on him if you don't.  
 Hope this helps.
Tammy