I had a look for what Johnny Raptor mentioned and found this which may be helpful..... http://books.google.co.uk/books?id=gszCU5xyJQQC&printsec=frontcover&dq=drawing+people Also check out Richard Smith's tutorial.... http://gnomonology.com/tutorial/343
Also you have a free tutorial by Scott Eaton on Pixologics website, he has a section dedicated to sculpting cloth that should help you out some more, check it out here http://www.pixologic.com/zclassroom/artistinaction/scotteaton/
wow thanks for all the answers and suggestions, i will take my time to look for all of them. In the meantime I played around with towels,t-shirts etc. I made a new Shirt(which is quite unfinished, but maybe it´s better then the last trys) As you can see, the left side is quite unattended, but that will change and hopefully…