Like the point of having someone on the ground. It's a good idea to make sure that person is more experienced than you so as to give any coaching necessary. Too many people who have never jumped before are attempting to teach a horse to jump, many without the proper guidance. You can't properly teach something if you don't know it yourself.
don't grab on to your horses mane when going over a jump it makes your form bad and it just looks bad.
Not true. It is better to grab a handful than get left behind on a green horse, which is unpredictable on how he will jump
The point here was that you are about to take a very green horse over, perhaps, its very first jump. It is only a wise precaution to grab a handful of mane. You are not in a show arena and needn't be worried about "form." Just hang onto your 'greenie' and enjoy the ride! Form and 'looking good' can come later. Just have a safe ride! :)