Source link: https://www.smooth-on.com/page/preparation-surfaces-epoxy-adhesive-bonding/
Porous materials are simple provided they are dry.
Surface should be sanded till clean and free from dust
Non-porous surfaces, e.g. metal and plastic materials
Surfaces should be degreased, dried, and roughened by sanding, sandblasting or chemical etching.
Avoiding Contamination of Prepared Surfaces:
Handlers should wear clean cotton gloves to prevent body oils from contaminating the clean surfaces
Contamination can be caused by a fingerprint, not perfectly clean clothing, or through the use of substandard degreasing or chemical solutions
For best results, surfaces can be prepared by three pretreatment procedures, which are listed by increasing effectiveness
Degrease only
Degrease, abrade, and degrease again
Degrease and chemically pretreat
Note:
It is more than sufficient to follow the provided instructions for an adhesive, i.e. read its technical data sheet. The source link provides very specific procedures for different materials. The procedures seem to be very specific and require technical expertise to perform. We would not resort to procedures researched online unless the technical data sheet of adhesives do not explicitly provide surface preparation instructions.