If you are a Linux user like me,you will find that they are few tutorials to install mods on Linux. The first thing you will need to do is install forge.Open minecraft launcher and click create profile select version 1.7.2 and name the profile 1.7.2. This is so Vanilla 1.7.2 has been installed as Forge requires vanilla to be installed to install itself. Now close the launcher.Go to files.minecraftforge.net to download the latest .jar installer. Choose the 1.7.2 version.Open the installer with java and then click install client then next. Wait for the process to finish.Now lets install a mod! Find a mod online DON'T GO ON DODGY WEBSITES Use planet minecraft for mods just to be safe.Download the .zip or .jar for your mod Open your home folder then select the view menu and show hidden files.There should be a .minecraft folder there open it and open the mods folder. IF MODS ISN'T THERE CREATE IT. Drag the mod into this folder. Run minecraft launcher and select the new forge profile. Now click play and your mod should be installed.

If mod doesn't work
-Check that the version is 1.7.2
-Check you don't need a core mod
-If your came crashes due to overlapping Entities contact the mod's develeper