When preparing homemade canned food, what are the the do and don't to avoid problems such as botulism ?

Hello everybody, me and my wife started recently to create our canned food, mostly jam and vegetables under oil. While botulism is really rare it can be fatal so we were wondering if there are some 100% sure do and don't to apply to avoid getting botulism from our homemade food. via /r/food http://ift.tt/2tyoAyQ