how to clear up space on hard drive of iMac

I am fairly new to the Mac system and I have found that my hard drive has filled up, I have deleted from Trash and from iphoto trash at least 100 GB of video and photo and it has not appeared to clear the space on the hard drive. I have had messages that I cannot update my software becasue there is not enough space on the drive.

I understand that there are local backups but I thought that the space would be freed up when needed, using the previously deleted files space, but this does not seem to be happening.

I am not using Time Machine, thought I do plan to do so.

From a search online it seems there are many different file types that I can go in and delete. I was hoping for a simpler solution as I do not have time or expertise to devote to doing this bit by bit. I know there is software out there to help, but I think there should be an easy solution supplied by Apple/Mac to clear up this space.

Thanks in advance for any assitance!