There are various ways to reduce friction:
1. By using lubricants: friction increases as the roughness of the surface increases. Lubricants fill the fine pores and gaps between contact surfaces and reduces friction
2. Polishing surfaces: It makes the surfaces even and hence reduces friction
3. By using ball bearings: Rotating machines can be mounted on ball bearings. Rolling friction is lesser than sliding friction
4. By streamlining: streamlining reduces the area of contact and thus reduces friction