Once you have completed your investigation at the scene, including any forensic crime scene processing, you should be able to turn control of the area back to the appropriate persons. You should make sure that you, or the forensic investigators remove all evidence, and equipment, and try to leave the area in the best condition possible under the circumstances.
In the event that you feel the need to return to the crime scene at a later time for further investigation, do not release the scene if at all possible. If you release the scene and then need to come back later on, you may first need to obtain a search warrant.
If you feel it necessary to keep control of the crime scene for a longer period of time, you will need to continue security. Certainly the best way to insure security is to station an officer at the scene. Secondarily, you may wish to post "crime scene-do not enter" signs on locked windows and doors, keeping in mind that this is the least secure method of keeping people from entering the scene. If, when you return, the seals have been broken, you can rest assured that any evidence that you subsequently retrieve will likely be precluded as evidence at any trial.
If you wish to maintain security over a crime scene for an extended period of time, i.e., days or weeks, you will more than likely need to apply for a court order granting you such control. You should consult with your department's legal bureau or the local prosecutor's office for assistance in such matters. Even in cases were decedents resided alone, there will be issues such as returning possession to a landlord, wills, probate filings, etc.
Homicide scenes are certainly the most emotional of all crime scenes, and how you leave the scene can have a dramatic effect if there are family members present. I recommend that all investigators read the The National Institute of Justice's Death Investigation: A Guide for the Scene Investigator, which provides excellent guidelines for dealing with a victim's family at death scenes.