No sneakers, no loafers, no work boots. No loafers because they can fall off your foot. No work boots because the lug soles can get caught in the stirrup and keep your foot from slipping out. Make sure you get your boots early enough to break them in. Make sure the pants you wear have smooth inside seams.
Most jeans have the heavy seam against the saddle and the smoother seam on the outside.
Wranglers and Santa Fe jeans usally have them with the smooth seam against the saddle. But don't think you have to wear jeans. Your old wool dress slacks that are shiny at the knees will actually work very well. So will khaki's that don't fit to tight or to baggy. Make sure your slacks are long enough as they will ride up while riding.