Summer guests....Start your hike early to avoid the crowds and to ensure parking (or take the Hiker Shuttle).
Make sure to be off the mountain by 2PM latest to avoid the afternoon thunderstorms.
Take plenty of water and snacks!!
Regarding favorite hikes...it is kind of hard to say without knowing how hard everyone is willing to work...but here are some of our favorites; various levels of fitness required and in no particular order:
Here is a good link where you can find all of these hikes and more! http://www.protrails.com/area/8/rocky-mountain-national-park