Word-of-mouth marketing is simply the phenomena where people tell other people about your product.
Mouth-of-word marketing takes time. You cannot control how fast the news travel. Don’t focus on doing tricks and ‘quick solutions’ to getting people to talk about your game. Advertising is okay, asked referrals are okay – but people who talk about your game will decide whether they talk about your game. You cannot decide what they will say. The only thing you can control is your product and how you present it. Concentrate on that.
The secret is: Focus on quality product. Whether it’s your blog, service or your game, the quality is the key. Think what products you have recommended to your friends. These products and services all share this common trait: they have been very useful to you and that’s why you recommend them to your friends. That’s where you have to aim as well: Give others something worth talk about.