I do not always write in my patterns about steaming before assembling.
Steaming plumps up your wool. It also helps to even the loops out.
I would do this step for every rug hooked project.
For really good instructions on how to do this I suggest this web site.
Another step I do not always put in my patterns is taping your finished piece. Take strips of packing tape and lay it over the rug and then pull it up. Use as many pieces as you need to until the tapes starts to come up clean when pressed onto the loops. This cleans off the fibers that were created when your strips were cut. This really helps.