the belts on my new(used) mazda protege are squealing...
how do i tell if they are too tight or too loose...?
..and what is the best way to change them?
do i loosen the Alt..or the puller closer to the front?

 

Spray some WD40 on them and see if the squealing goes away,if persist then you got to change them.

 

don't spray it with wd40 its key ingredient is fish oil it will squeel forever if you do thats why when you get anti freeze or anything on the belt you have to change it even oil you have to change the belt. you want the belt tight there is a thing called an idler pully its spring loaded so it will set the tightness for you, your best bet is to check the belt itself for wear thats most likely the problem if not try to pin point the squeeling in one of the pully's cause thats where it will be if it is squeeling and just change that pully