Kindly refer to the following link(s):
Why is it permissible to eat meat slaughtered by Christians & Jews, they don't say Bismillah
Eating meat slaughtered by Christians and Jews
Eating meat slaughtered by nowadays Christians and Jews
Zabiha vs. Non-Zabiha: Can we eat meat that's not slaughtered in non muslim countries?
The slaughtering of those who have corrupt Aqeedah
Can I eat food (meat) from my Sufi relatives who do shirk?
Ruling on Stunned Meat and Kosher Meat?
Can Muslims eat from McDonald's, Subway & Grocery stores in Non Muslim countries?
Eating non-vegetarian food in Mc Donald's, KFC etc in India
Can I trust a Hindu restaurant owner or waiter if he says the food is halal?
Also see: Stunned Meat Kosher