Usually, it comes down to following the way the intructor approaches the demos as well as studying the references you're pulling from. If you haven't looked at the informal demos, it might be a good idea to look into them now and hopefully they give you a better idea. It's not about capturing the reference precisely, it's about making the effort to lay in the forms you see - especially the leg construction and head construction in your case.

When constructing the legs, students often start with a chain of sausages and will add a few additional masses. In most cases though, these are very much limited to bumps that impact the silhouette, without much consideration for the masses that fall within the silhouette. These inner masses are just as important since they help the legs feel more grounded. The same can be said about the way they approach the head. They carve out the eye sockets, add the muzzle and that's it. These are good starting points don't get me wrong, but I think it's beneficial to think about these additional masses that's often seen in the informal demos section since they help hold everything together like a puzzle rather than fragmented pieces that are about to fall apart.

Also, I'd like to see the reference images you're using next time. That would help a good deal.