This is not bad:
stance: http://www.youtube.com/watch?v=9qZyDvDwOZw&feature=channel
jab: http://www.youtube.com/watch?v=gmZ0OAR_4BY&feature=channel
cross: http://www.youtube.com/watch?v=0PLRRXxxH6A&feature=channel
left hook: http://www.youtube.com/watch?v=4m8H9YEz888 < look at his other videos also
I throw a left hook with my thumb up but the mechanics are similar. Do what's more comfortable.
stance: http://www.youtube.com/watch?v=9qZyDvDwOZw&feature=channel
jab: http://www.youtube.com/watch?v=gmZ0OAR_4BY&feature=channel
cross: http://www.youtube.com/watch?v=0PLRRXxxH6A&feature=channel
left hook: http://www.youtube.com/watch?v=4m8H9YEz888 < look at his other videos also
I throw a left hook with my thumb up but the mechanics are similar. Do what's more comfortable.