This is a special post for the Ask Mike section based on a current local event.
As most of you have probably heard by now, within the last few weeks some deranged lunatic has been placing poisoned meatballs around San Francisco streets in hopes of killing neighborhood dogs. In fact, a number of dogs have been sickened and at least one has died. While there is no explaining why some people are driven to prey on the lives and emotions of innocent neighbors and their pets, thankfully there are many things you can do to protect your dog from such madness.
The first, of course, is vigilance. When out walking your dog survey the scene ahead of you and try to be as aware as possible of what you and your dog are approaching. Steer clear of suspicious items which would include any food items.
Second, be sure that your dog is well trained, at least with respect to leash walking and the command "off." Specifically, use whatever combination of gear and methodology you need to to ensure that your dog does not pull on the leash. If your dog is pulling madly on the leash it's guaranteed that a) he's in his own world and on the hunt, paying little if any attention to you; b) you're distracted by the pulling and thus much less able to be aware of things you might be approaching that could be dangerous to your dog and c) even if you are aware of such dangers you'll have fairly little control over your dog with which to effectively respond.
Additionally, be sure that your dog is very responsive to the command "off" or "leave it." Very responsive means that when you say it once in a commanding tone of voice your dog will back off from whatever he's focused on and turn his attention to you.
Lastly, DO NOT walk your dog around city streets without a leash on! Ever!!! People do this all the time and it absolutely drives me insane. Not only do dogs routinely get killed for this very stupid reason (over a hundred dogs I've worked with over the years have been killed by cars for this singular reason) but in relation to the question at hand, off leash your dog will be guaranteed to find that meatball or whatever else way before you have a chance to respond.
In short, be attentive and take the time to train your dog. It protects his life and your mental and emotional well-being.