The main way to make sure that your furniture works well together is to ensure that there is a common 'theme' running through each and every item that is in a particular space. The theme can be color texture style period of construction or something entirely different.
Less is more. The most important rule to remember when decorating any room is don't clutter. Less really is more. Choose simple pieces and keep the extras to a minimal. What decorations you do use don't over do it but rather select a few quality items.
This is not to say that all items need to be made in the same period have the same texture or be of the same color but instead that you should stick with a few themes and make sure that one or two are reflected in each and every piece of furniture that you have in your living room.