When one thinks of a salad bar, it is often assumed that the salad bar is gluten free. This is not always the case. Cross contamination with items such as croutons or other "toppings" is not as rare as one would hope. Not only that, but many salad dressings are not gluten free. This does not mean that you have to give up salad bars.
Here are a few hints to make your salad bar experience as safe as possible.
Look carefully in each item you are planning to get to make sure that there is nothing extra in there. In most cases, you will be able to see something like a crouton or a salad dressing splash. If this has occurred, then cut that item from your salad, at least until the item has been replaced.
Bring cross contamination to the attention of the staff. They may be able get you fresh ingredients so that you won't get sick.
Double check with the manager and the wait staff to find out what dressings are gluten free, in most cases you will probably not be allowed Thousand Island. The rest vary greatly. I know that a lot of restaurants use wheat in ranch and blue cheese; however, it really does vary.
Steer clear of the toppings bar. This is the easiest to get contaminated. Also, you might not see this contamination. People are not careful with the tongs and/or spoons at the topping side of the bar. This means that while the sunflower seeds are gluten free, the spoon may not be.
If in question, skip the salad bar and order a side salad the way you want it. There is no reason why you should get sick.