ArcGIS 10.1 Legend - Increase Icon on legend without increase on map

The method we use is to have a duplicate copy of the layer just for the legend. After the map layer looks the way you want, just drag the layer from the TOC and on to the map to make a duplicate. We append '_map' to the name of the map layer version to differentiate between the two layers. Then the symbology size or width can be adjusted for each icon or line as needed. Some symbols seem to need to be adjusted larger or smaller to make them look right compared to the others in the legend. This gives you the larger symbols but you retain the dynamic nature of the legend.

In the legend properties (accessed by double clicking on the legend) go to the layout tab and there is an option to adjust the patch width and height (see below). That should change it on the legend and not the map.

The alternative is to make the entire legend bigger if you are printing on A0.

An alternative would be to go to "Layout View", right-click on your legend, and "convert to graphics", then you can "ungroup", and resize each graphic as you see fit. It should work for making them bigger on your final print out