First, read the Fall of Reach, ALWAYS.
Then skip Halo: The Flood and play the first game. Halo: The Flood IS the first game, except some of the events that take place do not occur in the game. This book isn't canon and it is really... bland.
Next, read First Strike, this book is in between the first two games and ties the two together, also revealing how Sgt. Johnson survived the encounter with the flood.
After that play the second game, then read Ghosts of Onyx.
Play Halo 3: ODST and then Halo 3, and then continue reading with Halo: Contact Harvest.
Play Halo Wars as it takes place on harvest, then read Halo: Cole Protocol, and Halo: Evolution to learn more about the lore of the universe.
You can play Halo reach, but I would skip it if you want to learn more about the lore because Halo Reach, while it has a great story, directly contradicts the book. It is not canon in my eyes for this reason and also because Halo: Fall of Reach has a superior story to tell.
Read the Forerunner saga after that, Cryptum, Primordial, and Silentium, but keep in mind that they are a very... unique read. I love it, but many people are easily bored by it. The second book also has serious problems, so keep that in mind.
I always stop here, and for me, the quality of the stories and games go downhill significantly, but if you wish to continue, go to Halo Reach.
Play Halo 4, if you wish, but keep in mind that the Didact from the books and the didact from the games are significantly different characters in their military strategy and prowess.
Finally, skip the rest. It goes downhill, and only gets blander, duller, and less and less interesting.