Change your accent to that of a middle class person
Do not join groups of poor people such as gangs or any group that will pressurise you not to leave
If possible, move away from the poor environment even if it means moving to another poor environment. The essential thing is not to form relationships that cannot be easily broken.
Don't fall in love, or make any form of commitment that is difficult to break.
Don't get into debt.
Learn to dress well.
Take public speaking lessons and feel at ease in communicating with others.
Don't talk about coming from a poor background. It makes people feel uneasy.
Learn to speak slower and and lower, and think before you speak.
Don't use slang.
Avoid places and situations that you do not feel comfortable in.
Learn middle class mannerisms but don't overdo it.
Learn to live within your means, and don't pretend to be anything you are not.
Set yourself small goals to achieve that you can easily reach.
Keep a diary of your progress, and regularly review it to see what works and what does not work.
Observe people and see how they relate to each other.
Pick your friends carefully.
Do not waste time, money, or resources.
Don't be afraid to take risks, but make them calculated risks.
Have a plan, but don't be afraid to change it.
EDIT
Several comments on 'changing ones accent'
People who are not poor but in the performing arts such as actors, singers, etc. change their accents because it is necessary for their work
People who are not poor but have strong regional or foreign accents, commonly change their accents because it enables them to communicate better in thier work
People who are not poor but whose work requires them to speak in public or generally have to give orders, work on the phone, or broadly have to work verbally, will often change their accents because it helps them in their work
Quite often changing their dress style to be more appropriate to the work they do is common, even if one is not poor
Many people change their manner of speaking, dress mode, and behaviour in accordance with the company they are in
Such changes do not mean that one is presenting a false face to the world, it simply means that one is adopting the requirements of the work or the mannerisms of the social group one is in
It is little different from having to wear a uniform, as many jobs require, or to conform to certain work ethics that are known to be suited to the job
If you do happen to be poor AND ambitious, then learning these matters is a help.
If you happen to be poor and NOT ambitious, then you needn't bother
Being poor and ambitious does not mean leaving your family and close friends, but it probably requires leaving groups/gangs/teams that require you to retain your background mannerisims.
Studies of poor people who become successful show that they do not make attachments that limit their freedom of movement
The advice on 'get an education' is good advice if you are in a situation where you have the time to study, a place to study, the money to study, the friends to study with etc. And have no commitments, duties, obligations, etc. that detract from your studying
it would be interesting to know how many comments on this issue come from people who have been poor and eventually became successful.
By poor, I mean being brought up in a house that has no books in it, possibly with a single parent who has to work full time just to survive, and where they have no one who can advise or help them, and where any attempt to improve oneself is looked upon with derision, and further, where your ignorance is exploited by those who should know better
By successful I mean those who eventually achieve their goals in the sense that their name can be spoken and recognised with respect in the field they choose to work in.
