If your not creating the poster in illustrator, here's a few tips on fonts in photoshop. I would advise if you have illustrator to create the artwork in photoshop and then import the artwork into illustrator for the fonts to be crisp. It's not a required though.
What the fonts setting do for you in photoshop.
None - No anti-aliasing. Use this option for very small text, under 10-12 points.
Smooth - The average setting to make text appear smoother and easier to read. The highest setting of anti aliasing.
Crisp (default setting) - Results in slightly sharper edges than the the smooth option. A good happy medium between none and smooth.
Strong - Makes text appear heavier than the smooth option. But not like using a bold.
Sharp - Makes text sharp, but somewhere in between strong and crisp.
Anti aliasing example
But I just use illustrator! because I like my crisp vector fonts.
