Having the right ingredients is of the utmost importance when making classic tiki drinks. Without fresh juice, the appropriate rums, and exotic mixers, my drinks always came out less than impressive. It's not always easy to find these at your local store, however.
Fortunately, Trader Vic's sells their line of syrups online, so it's possible to get Orgeat (key for Mai Tais) anywhere in the country. Besides the orgeat, other key syrups: Grenadine (much thicker than the sugar water from Rose's), Rock Candy (also known as Simple Sugar), Passion Fruit, and Maraschino (yep, the juice that would normally found in a jar of cherries).
Prices range from $4.00 to $4.75. The only downside is the shipping costs—to Florida where I live, the shipping is almost as much as the product. But since it's the only way I can get what I need, I don't mind.