TEA: Any dark, rich, robust black tea will work best here. Assam, Darjeeling, etc. You can also make the tea part as strong as you like. Start with one tablespoon loose leaf tea and add more according to your taste. Use loose-leaf or tea bags.
SPICES: Whole spices are preferred here but in a pinch feel free to add or sub ground spices to taste. You can add the ground spices at the end if you like.
MILK RATIO: Instead of the full cup of milk, I typically use a ratio of ½ water and ½ milk. Many prefer the richness of a full cup milk, so feel free to adjust to your taste.
BATCH MAKING: You can make a big batch of the masala chai (without the milk) and refrigerate for up to 4 days, and heat up with the milk and sweetener when ready to serve.
You can add more whole spices and more black tea for an even stronger more concentrated version.
UPDATE: While in Northern India this past month, I had this Chai with the addition of a big handful of fresh mint leaves (simmering in the chai). ABSOLUTELY Delicious! Give it a try!