Depends a lot on the Plane.
For my Foamies, I use double sided foam tape. For the larger planes, I use some double sided tape to hold some foam to the mounting side of the unit, then use zip ties (With a little foam between the zip tie and the component) to secure it.

For Clevises
On the smaller planes with plastic clevises, I use a piece of fuel tubing over the clevis, for the larger planes, I use top quality clevises that do not require any additional help.