Sergio,
In my experience, the biggest factor in file-bloat is the mistake of File > Place -ing graphics without first opening them in Photoshop, adjusting the size/and/ppi to match the expected use size on the page in InDesign. In other words, a lot of images default to 72ppi. They benefit when you re-size them to the designed physical size, but also set the ppi to (usually) 300 ppi (common for printing). Doing this first, and then import/Place into InDesign allows InDesign to create much smaller image previews for the linked file. This directly affects file bloat.
Many say it is better to leave the original scan alone and do not down-sample it, and I agree with that. But you can still freely change the Image > Image Size ppi to something higher like 300 instead of 72ppi. This doesn't resample the image, allowing you to keep the original pixels. There is no image degradation; yet InDesign experiences less file bloat.
The other commenters have already also mentioned doing a Save-As from time to time. They have also mentioned doing an export to .IDML and re-opening the .IDML to a new, cleaner, InDesign file. File > Placing; not drag-n-dropping; not embedding; all those are good practices, too.
... View more