Before you actually start constructing your God, hire some seriously good copywriters to invent a name for your religion. Take care not to annoy mainstream religions like Judaism, Christianity, Islam, Democracy or Apple by imitating their names, trade and/or service marks. Your god may have mercy; their lawyers don't.
This is undoubtedly the most determinative part. The generally accepted practice for the last 4,000 years is to avoid multiple gods and concentrate on one almighty being. In the long run this approach is far more flexible, provided that your God is immortal and avoids contact with anyone but you.
In order to make a viable god you will have to spend a good deal of time observing potential clients. Do your neighbors love football? Then proclaim that the universe was created within 90 minutes by the God aided by 22 angels. Do they love porn? Then borrow a lot from Greek mythology where gods never missed an opportunity to have bizarre sex. Do they enjoy music? Tell them that your God's primary creation tool is the E#m chord. Don't be lazy! Never forget to give them what they want—and they will keep bringing you all of their possessions.
The principal reason to design and build your own God is explained in the next section.