I've been playing poker for a while, and against casual players, I'm fairly good. When I mean casual players, I mean co-workers (even those that are "serious" about poker), random poker parties, against other tourists in Las Vegas, etc. I do this by playing relatively conservatively, playing my cards and not the players, and rarely bluffing.
However, I know that when I play against even a semi-accomplished player that knows how to bet aggressively, I'm out of my league. Because I play conservatively, it doesn't take a lot to chase me out of a pot.
How do I take my game to the next level and improve my style of play to incorporate more bluffing, more aggressive better, etc, without losing my shirt with real money? I unfortunately don't have access to real-money online poker being in the US.