You can get USGS topos free online at libremap.org. For day hikes, it's cheap to download the USGS, cut out a section, and print it out. But you do have to be careful to preserve relevant info like scale, datum, magnetic declination, and UTM grid. For medium-length hikes, it works better to just order the full-size sheets from USGS. For hikes that cover longer distances, it becomes impractical to carry that many 1:24,000 maps, so it's better if you can find something like a 1:63,360 Harrison map.
I wouldn't trust google earth or google maps as a primary source of info, but it can be helpful for trip planning. If you're using a USGS topo without contour shading, it can be helpful to compare with a contour-shaded view from google maps; it really makes the topography "pop" visually. It can also be handy to get a google earth rendering of what the landscape will look like from the ground, e.g., will I be able to see this saddle from this peak.