In addition to 3D warehouse components, which are often ‘heavy’ with added detail and or materials, you can check all materials (and their sizes) in your file using the Material Tools Extension. This way you can edit any too large textures.
Also make sure that you are using components for all repeating elements. Make sure that your model is near the origin. Lots of things to check…try searching the forum for other ideas as this is a reoccurring need. For example: Reduce a file in size - #12 by boardumb