Dedicating one's soul to Satan is not a trade. You are not "selling" your soul. In fact, it should be a purely unselfish act on your part. You should expect nothing for doing it, except an afterlife filled with peace, love, and everlasting bliss. This does not mean that you will not be rewarded in this life. Satan has rewarded me IMMENSELY in many ways. The point to make though, is that you should not have *expectations* of immediate reward. If you think that by dedicating your soul today will make it so that tomorrow you win the lottery, start dating Angelina Jolie, and kill all of your enemies by pointing at them then you are seriously fooling yourself. Dedicating your soul is about reaching out to your creator and acknowledging Him as the Father of humanity and entering into a spiritual bond with Him that lasts forever.
It doesnt matter when you do your dedication, but there are certain times that can yield immediate feedback. I prefer the dedication be done in the phase of a new moon, to symbolize a new chapter in your life. Days that are special to you, such as your birthday are good days to do a dedication. Also, days that are special to Satan: February 4 (Candlemas), March 21-23 (Spring Equinox), April 30-May 1 (Beltane), June 21-23 (Summer Solstice), August 1 (Lammas), September 21-23 (Autumn Equinox), October 31 (Hallowmas), and December 21-23 (Winter Solstice). The benefit of dedicating on these days is that there is a lot of Satanic energy in the atmosphere. Many people are performing rituals, and a lot of POSITIVE energy is invoked and exchanged.
When you perform your dedication ritual, I recommend bathing prior to the ritual and performing the ritual in the nude. You do not HAVE to do this, but you should try to put your body in as close to a state of cleanliness, perfection, and birth (without the "sins" of false religions that have been thrust upon you in everyday life). Burning incense (Myrrh and Dragonsblood are good) and lighting black candles are beneficial as well. Again, these are not necessities - you are simply trying to evoke as many energies that might be beneficial to you. The more energy you can use, the more likely you are to physically "bond" with Satan. Now you should write the following on paper: "Before the almighty and ineffable Lord Satan and in the presence of all Demons of Hell, who are the True and the Original gods, I, (state your full name) renounce any and all past allegiances, and proclaim Satan Lucifer as my one and only God. I promise to recognize and honor him in all things, without reservation, desiring in return, his manifold assistance in the successful completion of my endeavors." You should sign this pledge in blood. The purpose of the blood is to "give back" the DNA that Satan originally implanted you with. I recommend cutting your arm with a CLEAN razor or needle and pushing your LEFT index finger into the blood and pressing your left index finger print onto the bottom of the paper. It should leave a fingerprint in blood. Your fingerprint and your DNA is unique to you but is tied genetically to Satan. Read the pledge aloud and then burn it in a candle. The purpose of burning it is not to cause a fire (so be careful) but to TRANSFER the energy from the paper to the elements (in this case, fire, the air and the earth). Whatever is left after burning should be given back to the earth through burial. Finally, (and this is a very important step) you should meditate. This is where you privately ask Satan for help and guidance through the difficult times that you will undoubtable encounter (as we all do in life). This was the point in my dedication that I physically saw Satan appear before me. This does not mean that you will see Satan appear before you. We all have different levels of openness and communicative abilities. But live the rest of your life intelligently and following Satan's wishes (He will communicate them to you in time) and you will be greatly rewarded.