Resampling means adding or removing pixels. When adding (sizing up) for images use BiCubic Smoother. For sizing down, BiCubic Sharper. In CS6, the new Auto setting in Preferences will automatically select this when it ‘see’s you are sizing up or down. In the old days, you had to manually select this.
In terms of best practices for sizing up, this should help:http://www.digitalphotopro.com/technique/software-technique/the-art-of-the-up-res.html?start=1