If you have asked the person out on a date with you but she refused, you should try to figure out the reason of rejection. Stalking her all the time will not help you but try to identify the problem as this is the key. You should think of all the possible reasons she refused to hang out with you.
If you want to stalk her, you better stay updated as the right timing does matter in the accomplishment of tasks, provided that adequate effort is made. Try to find out her daily schedule and then adjust your routine accordingly.
Make sure that you are present at every place where she goes.
Try making a strong eye contact with her as this helps in most of the cases.
You should try contacting her as much as possible. Keep a close eye on everything she does.
You should consider sending unidentified love mail to her.