There are tutorials covering the basics of making all the parts of a Pre Heresy terminator but each one only covers the making of one style of part. Using the Techniques covered in those tutorials and a few different parts you can easily create a bit of variety in your models
Helms 
This one is a normal Marine helm filed down quite drastically so it fits flush into the head recess-this is based on the old "Exo Armour" Terminator Models and the artwork in the Original Space Hulk Rule Books
This one uses a Chaos Aspiring Champion helm With the horns etc removed. Extra banding is used around the Head recess. Again this is based on the early "Exo Armour" models
These two are exactly the same as the one in the Helm Tutorial but one has no banding and the other has extra banding-just variations on the same theme
Arms 
Instead of building up the under armour from Plasticard this "quick" variation uses a Terminator shoulderpad guled the other way round to create the lower level, the spacer and top level are made as in the tutorial. A band of Plasticard is put round the edge of the pad to add a little detail and cover the "cut outs" that are there.
As above but with extra banding and leather tassles made from thin strips of plasticard glued to the underside of the shoulderpad