How to Design a Successful Religion?
Firstly, your religion should apply to some very basic instincts of humans. Good candidates are love, hate, fear, sociality, and greed. Generally fear, most prominently the fear of death, is the best candidate - hence remember to promise a paradise of some sort for those who worship your religion most deeply and hell or Guantanamo Bay for those who don't.
For centuries religions and entertainment were deeply intertwined, but this coupling is decreasing. I suggest you do concoct holy scriptures with many charismatic figures, heroic tales, vague metaphors, mysticism, and descriptions of wrath of your deities, but otherwise allow your worshipers watch television, use mobile phones and surf the net as long as you get a few hours a week and twenty minutes every day. Otherwise your religion won't be compatible with contemporary culture, which may mean that following your religion will be hard for some age groups.
Secondly, just like drugs, make your religion easy to become acquainted to but require at least some devotion to fully comply. The best compromise means that it is possibly to learn and try your religion without taking the possible social pressure of giving up one's current religion, but once devoted, gives as little chance as possible to pick up yet another religion. Note, however, that redemption for the fallen should be possible (even if perhaps uncertain), otherwise people won't return to your faith once they've lost contact with it.
Thirdly, remember that religion and evolution have a deeper connection than some religions trying to deny evolution. Specifically, unless your religion supports its practitioner's survival and procreation, your religion will simply die out - this has happened numerous times for many strange sects in history and most evidently in various cult suicides. Features such as religious upbringing, conversion, and even religious wars increase your religion's chances of being the fittest.
But even in peaceful times memes, including religion, experience evolution and people pick memes more frequently from those who have succeeded well in the society. Hence, I suggest you add an element of pre-death revenue: one's success in society is at least partly god's grant for one's devotion to your religion (while someone faithful but unsuccessful in society might still only going through the equivalents of god's tests to Job).
If I had a lot of extra time, I'ld probably make this easy for you, oh future prophet: I've considered writing a web page which asks a number of questions (for example the religion's position on various issues such as emphasis on love versus hate), and automatically create a holy scripture of desired length using a context-free grammar.