Make sure to arrive early (7/8 am) or later (after 5 pm) to avoid the crowds. If you go during the busiest times of the day, there may not be parking available and you might be turned away. There is an easy walking trail along the shoreline with incredible views of the lake and mountains.
Feel free to explore the beautiful Fairmont Banff Springs, it is open to the public even if you aren't staying there.