To get a stronger coffee is really simple. You need more ground coffee to make the final result stronger.
A weak coffee in a breakfast restaurant might use 5 grams of coffee per cup. In a coffee shop, they might use 7 grams to give you a fuller flavour. A shot of esspresso would use about 9 grams of coffee per cup. Some of the more upscale coffee shops use even more coffee -- such as 12 grams for a large cup of coffee at Starbucks. Basically strong flavoured coffee simply requires more coffee beans per cup!