What a fantastic question.
Exercise - Yes. Exercise is good for you because it helps remodel and strengthen bones, especially walking. By doing this calcium is able to enter bones. Sometimes, kidney patients have too much calcium in their system. If it cannot deposit in bones, it may deposit in blood vessels. This is known as vascular calcification.
Secondly, exercise helps reduce inflammation. Inflammation stimulates many adverse processes in the body - and can damage your blood vessels and your heart.
Cigarettes - Smoking is bad for you. This unnatural substance must be handled by body tissues, and stimulats hardening of the arteries. It causes pulmonary disease, and it causes cancer. In addition, it has been linked to advancing chronic kidney disease.
Diet - The diet a physician will recommend may depend upon the underlying cause of kidney disease. In general, controlling one's blood sugar through the reduction of sugar and carbs will help promote healthier blood vessel walls and less inflammation. Diabetes ensues when one regularly ingests excess sugar, essentially reducing the insulin-producing cells in the pancreas. Over time glucose intolerance develops. Many persons who eat excessively have a delay in insulin production. This may cause hunger, several hours later, enabling poor eating habits.
Salt may also be bad in that it increased blood vessel tone and may worsen blood pressure. We generally do not restrict fluids, but let thirst dictate how much one drinks. If one eats excessive salt, thirst will increase. Fluid gains will promote high blood pressure. Salt balance is also related to potassium balance. The ability to reabsorb salt by the kidneys may be genetic. Hence some patients will become hypertensive on the same salt (sodium) intake while others will have normal blood pressure.
Some tribes in South America have never been exposed to salt in their diets, and have very little hypertension, gout or other related diseases. This theme has recurred in other countries where there are indigenous peoples who never had the misfortune of being exposed to excessive salt. Our diets are unfortunately high in salt; it is a food preservative, and an adjunct to flavor. Hence we have a very high incidence of hypertension and consequently of stroke, heart and kidney disease.
I hope that this answer will be helpful. But, changing a lifestyle is a very difficult and challenging process.