There is a well known segula for parnasa, to say Parshas Hamon, http://www.718insurance.com/pdf/parnasah.pdf "shnayim mikra ve'eched targum" (2 times the posuk and 1 time the Targum Unkelos), on the Tuesday before Parshas Beshalach is read. The source of this custom is Reb Menachem Mendel of Rimanov, one of the four primary disciples of the Noam Elimelech. Reb Sholom of Stropkov used to say this over in the name of the Rimanover. Reb Mendel of Rimanov expounded on Parshas Hamon for 22 years; many of these explanations are available in print. It is therefore understandable that he is the source of this minhag; if anyone really understood the meaning of Parshas Hamon, it was him. http://www.tefillos.com/parshas_hamon.asp
The halachic works say that it is a good thing to read Parshas Hamon everyday. (Tur 1; Shulchan Aruch, Orach Chaim 1:5; Aruch Hashulchan 1:22; Shulchan Aruch HaRav 1:9). Shevet Mussar says that the segula of Parshas Hamon is when it's read "shnayim mikra ve'eched targum" and Siddur Segulas Yisroel says to say it with the cantillation. The common custom seems to be to read each posuk once, without cantillation, aside from the Tuesday of Beshalach.
Mishna Berura quotes the Yerushalmi in Brochos that says one who says Parshas Haman will not lack sustenance, and quoting the Taz says that reading it alone isn't sufficient, but one has to understand from the reading that our sustenance come about through Divine intervention. By reading the account of how Klal Yisroel was sustained by Hashem in the desert for 40 years, we ingrain in ourselves that our livelihood comes about only because Hashem wills it. So, if one reads Parshas Hamon religiously and despite this feels the need to cheat or lie to make a living, he did not learn anything from Parshas Hamon. It's not a magic incantation but an affirmation of Hashem being the "Hand that feeds us". (Remember the Kav Hayosher says that one who is honest in business is a complete tzadik.)http://zchusavos.blogspot.com/2007/08/who-is-tzadik-gamur.html
The great Mashgiach of Lakewood, Rav Matisyahu Salomon shlita was asked how there are some people that daven so intensely and in their business they treat employees and associates in such a horrible manner. He answered that when these people say "Boreich Aleinu" in Shemonah Esrei, they are thinking: "Hashem, I'm a pretty smart guy and developed a successful business. Please don't interfere and mess things up." That is how these people who seem to daven so "ehrlich" in the morning go into their offices and treat everyone like trash; they think it's their smarts making the money and don't really believe that all is from Hashem.
The Orchos Tzadikim (Shaar HaAnavah) says that there are three reasons why Hashem gives people wealth: 1) As a reward. These are people that use their money for good causes and will nevert hurt others with their wealth.) 2) As a test. How will they handle the money? 3) As Nekamah (revenge). These are the people who are wealthy and take advantage and trample over those not as fortunate.) I believe that when we work and think that it's our own smarts that make us money that puts us in category 3 – a punishment, because if we don't realize that it's Hashem giving us the money we will probably not handle it correctly. When we acknowledge that all our livelihood comes from Hashem, such as by reciting Parshas Hamon, we can put ourselves into the category 1 – a reward, because by realizing that Hashem gives us whatever we have, we have a better chance of handling the money properly.
On the Tuesday of Parshas Beshalach, many people read it in middle of Chazoras Hashatz or other parts of davening. You will lose more than you gain by this. Parshas Hamon is a sort of extra credit, but listening to Chazaras Hashatz is required (this deserves a whole article by itself). Don't make a mistake of doing a segula at the expense of actual Halacha; following Halacha is the #1 segula for everything. And don't forget the main thing is the belief that no matter how smart it seems we are, every single penny is from Hashem.