The old Index Astartes article on Salamanders described their insignia. The left shoulder pad has the chapter symbol. The colors used on this shoulder pad indicate company:
1st/2nd Company: white insignia on black background
3rd company: oranage insignia on black bacground
4th company: green insignia on black bacground
5th company (reserve): black insignia on yellow background
6th company (reserve): green insignia on yellow background
7th company (scout): black insignia on white background
For my personal army, I changed the scout colors, giving the scouts the same chapter insignia as the rest of the army (mine are 3rd company), and making their right shoulder pad white with a 7 (from the space wolves decal sheet) to indicate their scout company status.
Squad numbers are displayed on the right knee. A flame or hammer honor marking may be displayed on the left knee. You can also paint flames on the lower legs as an alternative marking. I use a single flame to indicate sergeant status, and a single hammer to indicate veteran status. Senior officers may have crossed hammers.
The right shoulder pad has a flame insignia on it. Salamanders do not use the same squad markings as other chapters. Scouts have some sort of stylized mark in the IA article which I can't really describe to you. Example flame insignia can be found in Index Astartes or Codex: Armegeddon. For my personal, I used different flame insignia to indicate tactical, assault, and devastator squads.