Copy files to USB drive on PC (Windows Explorer). Connect USB drive to Mac. Copy over using Mac Finder.
Email should be IMAP, so that is handled. Contacts >> export as CSV and import into Mac Mail (if you are using that).
Bookmarks from Chrome and FireFox can be straight exported / imported.
Files (documents, pictures, music) are just files... you will need the equivalent program to open / view them on a Mac (ie., Microsoft Word on PC ~= Microsoft Word on Mac).
Not sure if I am missing something in your question... but this should be dead simple. Unless you are doing dozens of systems, don't try to automate it... faster and simpler to do it manually.