It took me long time trial and error to grasp the growing technique. Internet was unavailable 20 years ago.
What I do:
Soil: sandy or at least good drainage. Nutrient rich premix, such as black soil, must be mixed with sand to attain drainage and reduce water holding capacity. Rule of thumb is that a flooded pot should have its surface dried naturally in 2 days.
Water: twice a week. Took me years to educate my parents stopped in "helping" to water. They just can't stand the temptation to water a pot in drought.
Light: strong indirect sunlight with direct sunlight parts of a day. Inadequate light usually causes the plant to grow thinner and lengthened. Round cactus would be out of shape.
Fertilizer: non-urea inorganic, such as those used for orchids, 1/2 the strength.
These are just what I do. Do adjust according to your plants' condition. Over time, they will flower when it is in the right size and healthy condition.
By the way, marvin is correct that the branches can be rooted for another plant. Just that some species tend to branch too many than I care to replant. Some would even root in the same pot leaving them there. But I never put it in water for rooting, I believe it rots instead. Keep in the same condition as the adult plant will do.