If using tea leaves steep them in the water for 2 - 4 minutes to get the desired flavor in the brew.
The tea you are using makes a lot of difference. Assam tea is stronger than Darjeeling tea and is thus preferred by many tea enthusiasts.
The amount of milk should be well-balanced. Too much can completely alter the taste, too less milk can make it watery.
More amount of spices can keep your body warm during winter season. You can reduce the quantity in summer to maintain your body heat.