Applying a wood conditioner or a shellac seal coat prior to staining provides a barrier between the wood and the stain. This will help minimize the blotchy effect. Also, try a gel stain verses a penetrating stain. A penetrating stain is designed to absorb into the wood, and this does not work well with maple.As with all finishing projects, test the desired finish on a piece of scrap wood before you begin to stain. Try different conditioners and stains to produce the desired effect. Investing a few dollars and a little time on products to get the best quality will pay a big return when staining an entire stair. Staining your maple stairs takes patience. But the time invested to do it right will reward you with years of enjoyment and beauty.