When eating at a restaurant, I used to order non-vegan entrees, and specify that they be made vegan by removing or substituting their non-vegan ingredients. However, the problem I kept encountering is that these substitutions would sometimes be forgotten, and the food would come out with animal products in it. This would happen about one in three times. Sending the food back is no good, because the point is for animal products to not be used in the first place. At that point, I would simply accept that the damage was done, and eat it. I don't blame the cooks; restaurant work is extremely hectic, so it is only natural that special ingredient substitutions sometimes slip between the cracks.

To remedy this problem, I now only order food from restaurants that is vegan by default. If that means I can only order a salad, or if I can't order anything at all, so be it. It's simply too risky to hope that the cook sees your ingredient substitution.