There are a few things everyone should do before buying any product.
The most important thing is, however, to read what you're buying.
So, please follow these steps to make the world better:

1) Find out the country of orrigin!
This way you can boycott, for example, the Mexican tuna fish.
If you buy Mexican tuna fish, you are a dolphin killer!

2) Read the nutrition facts!
If a product doesn't have the nutrition facts, most likely the producer doesn't want you to know what's in it. Don't buy such product, even if it's cheaper!
Would you risk your life for a few cents?!

3) Find out who's the producer!
In today's society, a meal has to travel 6000 miles to get into your kitchen. This causes a massive pollution, mostly due to the long transportation. However, if you buy food from your local producer, the food has to travel less than 200 miles, it's usually healthier, and you support your local community.
Buy from your local producer-save the planet!