Okay I will type down few thing about feeding them. wolf should be eating meat but however, to be sure, open character info--pets--pet(he need to be active not dissmised), so you will see a smiley(red very hungry/yellow hungry/green fed, however even if it is green u can give him 2 more bites to be sure it is 100%), when you go mouseover that smiley there you can see the type of food, which your pet like to eat, another thing is, that you should pay atention if the level of mob, you have taken food from, is not higher level then your pet, the food you buy from vendor should also have the lvl of food scribed. It happens that he simply doesn't like that specific food, so try to get some other, usually meat from vendor work good enough or random beasts, just pay atention for level of food, it should always be around the level of you pet but not higher. 5-10 levels lower should still be fine. Between each bite he eats, there is around 10 second cooldown. If you dont use interface addons, you should see that smiley icon beside the icon of your pet too, and it should indicate the happiness too. Some interface addons (xperl,zperl etc etc) don't always show the happiness, you need to set it up in the options. however anytime your pet dies, get dismissed etc, he will be hungry, so if you don't have indication, be sure to feed him before you do dungeons or fight bosses.
*Can you also tell me what expansion and server are you on ?