WHO TOASTS AND WHEN
Traditionally, the host or hostess offers the first toast, the more informal the occasion, however, the less this "rule" applies. Around a dinner table with friends, a guest can propose the first toast (and often does), usually as a way of thanking the host for bringing everyone together.
The only real guideline is to make sure that all the glasses are filled before toasting. The glasses don't have to hold champagne or wine or any other alcoholic beverage; it's perfectly fine for nondrinkers to toast with water, juice, or a soft drink. Even an empty glass is better than nothing.
The "host toasts first" rule does still apply at receptions and other large functions (though the best man usually leads the toasting at a wedding reception).