Two major differences from the american way of salad: first, salad is a side dish, eaten with the main course, not as an appetizer. That means it's light. Second, no dressing (unless you run into one of those who look up recipes on the web and find only western ones). The so-called russian salad (with mayonnaise, potatoes, boiled eggs, green peas and some diced meat) is an exception.
It's mostly seasonal - if it's not, I wouldn't recommend it. You may get tomatoes in the wrong time of the year, but then they are either fast ripened in a greenhouse, or chemically treated to ripen by force - they won't have the taste and you're risking any side effects - just like anywhere else.
Salad (salata) is, accidentally, homonymous with lettuce (salata, zelena salata - green lettuce), which means that lettuce is the preferred vegetable, and it also suits the weather: it grows from early spring to late autumn, tasting more or less the same. It is darker and more tasty than your standard romaine.
Chopped onions, sliced bell peppers, cucumbers, shredded cabbage are the next common ingredient. Also, frequently, hot peppers - but these are usually served separately. Although Serbia is one of the countries where they like it hot, there are still many people who don't - or can't, because they are kids or have developed a digestional malfunction and mustn't.
As for seasoning, it traditionally uses some oil (preferrably sunflower - canola is not popular unless you're a railway lantern) and vinegar (wine or apple vinegar; the industrial alcoholic vinegar was once the only one you could buy in a grocery but it was quickly abandoned when others became available); maybe a bit of sugar or honey, a pinch of finely chopped garlic.
Between late fall and early spring, it's the winter preserves, aka turšija.