It's occurred to me that most coffee connoiseurship guides don't acknoweldge the fact that many—if not most—coffee drinkers take some sort of creamer and/or sweetener in their coffee. I'd like to break down that wall of (possible) snobbishness and collect a few random suggestions.
General, and most important, suggestion: unless you're having the same variety of coffee every day, take a couple sips of the black coffee before adding anything. That way you can get an idea for what it might need.
Sweetened (vanilla-flavor etc.) soy milk - best for espresso drinks, due to the moderate natural sweetness of the espresso.
Unsweetened soy milk - best for chai (Oregon Chai and the like), due to the very sweet taste of the chai. You don't need the milk to supply any extra sweetness at all.
Half-and-half - best for bright coffees like Latin Americans (those from Costa Rica, Nicaragua etc.). The coffee needs to cut through the fat content here. I find that espresso gets lost in anything fattier than 2% milk.
