Follow instructions on the paint container, They are there for a reason. 80% of painting is preparation.
Clean the surface to be painted very well. Mix the paint before use. Do not mix the paint with water or any other chemicals. That will dilute the chemicals used to manufacture the paint.
Use masking tape to cover the areas you do not want to touch with the paint you are using. Use drop sheets (plastic covers) to cover the floor to avoid drips of paint all over the floor. Avoid dark colours for interior walls. They make small rooms look even smaller and dark. Quality of your plaster is critical.Ensure your builders use right quality and quantity of cement during construction.