Before promoting an ICO, you have to make sure that your ICO has been prepared well enough to attract potential investors. Why? Because I believe you don't want to spend a lot of money doing promotion but your ICO doesn't offer something valuable.

A good ICO usually doesn't really need an aggressive promotion because usually it creates hype. However, I think every ICO should offer bounty rewards to get supporters from the blockchain community. This kind of promotion is cheaper and more efficient.