HOW DO GO ABOUT CONNECTING SCART LEADS CORRECTLY?

I run a skybox as well as a separate free to air decoder from 1 motorised satellite dish. I also have a DVD/Video combi all linked to same TV
How do I connect all the SCARTS so I can
1) watch SKY when required
2) watch Free to air channels when required
3) watch prerecorded DVD/VHS Videos when required
4) record onto Video from SKY Or free to air decoder