#1.
Friends-of-friends. If players have a good time, they'll invite others. Oftentimes I've told players "glad you enjoyed the game, help it grow and spread the word". When you feel like you're constantly nagging players about this, you're
almost nagging them enough.
#2.
Be a host. These are your guests. Give them a spread. Snacks, pizza, etc. 3 words: Hot. Dog. Roller. I've always used BYOB, so people can choose their own poison. But I've always got beer in the fridge. I have several who offer to bring things, which is great. I never knew I liked spinach dip until one of my players stepped up.
#3.
Tournaments. As
@Poker Zombie stated, cash games are going to scare off casual gamblers. You need casual gamblers. Far more people are willing to blow $20-40 on a night's entertainment than want to be hardcore gamblers. Once you pay the entry, there's no more "money management" to concern yourself with. Except maybe that rebuy...
#4.
Meetup. I've had a great deal of success with this. Create a group at meetup.com. About 25% of the people who join the meetup will actually show up to a game. You'll probably pick up 2-4 people, then see Rule 1. Meetup charges monthly, so I'll only leave it up for a month or two. Once they come to the game, I get them on our game's regular distribution list.
#5.
Scheduling. How often do you play? How do you notify players? A steady schedule helps the game become part of your players routine. Routines are good for attendance. Don't change/cancel your game unless someone is dying or you have fewer than 5 players. For notification, I use a group webpage, Facebook and the Band app. Its nearly impossible to get everyone on the same platform, but do your best.
#6.
If you game isn't growing, its dying. I know my game is humming when I have 8-10 die hards who want to play every month, and another 8-10 casual players who show up occasionally. That will consistently give me 12-15 players for each tourney.