My whole family hunts including me, at times we have as many as 20 deer in the freezer. You can tell a sick animal most of the time. Around here, the deer cut themselves on fences and a lot of times these get infected and form huge masses. If we find one of those on an animal we don't eat it!! If the deer is acting funny, we don't eat it.
As for cooking it, there are a lot of tricks to make it taste less wild. I soak der meat overnight in water in the frige, and it taste just like steak the next day. SOme people use salt water or buttmilk. We mainly tenderize deer steak and eat it chicken fried. We also cut it into chunks and it it in the rotisserie as kabobs. We do deer sausage and deer ground meat. We also use the trimmings as fajitas and stew meat, and for things like beef tips and carne guasada.
I grew up eating deer to the point that I can remember my first steak. I also remember that it didn't taste very good to me, it seemed to not have any flavor!!! I raised my whole family on it and can't imagine not having that source of free meat. My children are all grown now, so I don't need as many myself, but between all of us, we need more than ever. They all fill their freezers also. Right now, I am canning up all the leftover meat from last year since season starts soon, that way, if we have a bad deer year, we will still have plenty of meat!!