The most important thing is your appearance. You must work on your personality and try to look rich. Try to buy branded clothes and accessories. You must not ignore your shoes and other stuff as they also give a statement about your status. However, it does not mean that you just enter a branded store and empty your pocket. Try to find discount stores or you can buy second-hand stuff from different online stores.
You must talk like rich people do. Do not indulge yourself in petty issues rather pay attention to things that have some significance in your life. Mostly, rich people talk about business activities, global issues, latest fashion trends, exotic places etc. You must travel a lot to broaden your exposure, if you cannot, internet is your best friend.
Develop your interaction skills:
You must be impressive enough to divert others' attention from your origin. Make yourself well equipped with answers by reading a lot. You should also focus on your speech. Do not ever use slang and wicked vocabulary. Try to build a sophisticated accent and vocabulary. You may browse internet, read newspapers or watch movies for this purpose.
Carry yourself properly:
Now, when you have gone through the preparations, it is very important to carry yourself in proper manner. Be nice and polite but show too much leniency. Similarly, having an attitude is not a bad thing but you must not be rude. Be yourself and have a relaxed and upright posture.
Follow sports or hobbies of upper class:
Last but not the least; you should follow sports or hobbies of upper class. Consider golf, tennis, yachting, riding etc.