One point not mentioned above was grain direction. In my experience every piece of wood will plane easier from one direction than it will from the other. You need to read the grain and plane so the grain ends exposed on the surface are leaning --> /////// not --->\\\\\\ . Also take a paraffin candle and scribble on the sole of your plane every few strokes. You will be amazed at how it reduces the friction and makes planing easier.