Conservation of tooth structure during biomechanical preparation of crown can be done by
Tooth structure is conserved by using the following guidelines: 

Use of partial-coverage rather than completecoverage restorations.
Preparation of teeth with the minimum practical convergence angle (taper) between axial walls.
Preparation of the occlusal surface so reduction follows the anatomic planes to give uniform thickness in the restoration.
Preparation of the axial surfaces so tooth structure is removed evenly; if necessary, teeth should be orthodontically repositioned.
Selection of a conservative margin compatible with the other principles of tooth preparation.
Avoidance of unnecessary apical extension of the preparation.
Use of partial-coverage restorations
Minimum practical convergence angle (taper) between axial walls
Preparation of the occlusal surface, so reduction follows the anatomic planes
All of the above