The best pressure to run, is what the book specifies. If you do not have the owner's manual, try the FSM, from the home page of this site. There were variations in tire pressure, based on model/year, so, again, the book is your friend.
There have been discussions on what tires to buy, so if you are looking for recommendations, check out the
Pirelli MT66 Route tires. They have plenty of customer comments available to read (search the Internet for reviews). I believe they are sold just about everywhere, but I could be wrong. They are tubeless, but I run tubes in them, and have done so for five years, riding two-up, full saddlebags, full trunk, and a full tank bag, in the rain -- superb tire, only thing I run on, on three different bikes, including my heavy Voyager touring machine! Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII