Just got an iMac, after 20 years using a PC. Can someone tell me please, what is the proper, or best way to import my photos from the old PC? I plan to do it using a memory stick, but is there a default location to 'drag and drop' them to, or should I open a piece of software to do it? I would like to be able to view the photos in iPhoto, but also have them available in iTunes to sync with my mobile devices. What is the best thing for me to do?

The default location for Safari to save an image from a Web page if you right-click and choose "Set as Desktop Background" is:
/Users /yourhomefolder /Pictures

Otherwise, you can put them anywhere you like other than the /Library or the /System directories.

iPhoto (recent versions) can find photos anywhere, but if you set the iPhoto preferences for "Copy items to the iPhoto Library", they go to a folder called "Originals" inside the iPhoto Library bundle. The default pathway is:
/Users /yourhomefolder /Pictures /iPhoto Library

A bundle is a special-purpose folder in OS X. It is a concept brought in by Steve Jobs and his gang of NeXTSTEP engineers. It serves several purposes, such as hiding access to a group of files that need to remain together. Messing about in the iPhoto Library bundle can create havoc with the way iPhoto handles your photos.