Just got myself a 5D MarkIII for the very same thing recently, so there will be similarities because we have the same lens. Been doing landscapes for a wee while now.
I find using a really sturdy tripod as others have said. Using Live view is important too, pressing the info button a few times to get the histogram up too really helps you keep control of the darks and lights. Most of the time you'll be doing a blend of several images. It's sometimes unavoidable in landscape.
I've always been taught to light a landscape from the side, and I bought a B+W circulating polarizing filter to help with glare and haze.
Landscapes are about great background work, and less about the gear. Using the Photographers Ephemeris app is extremely helpful. Scout out a location you want to visit. Look at it on Google Earth first, then check the Photographers ephemeris for the times that the sun rises, and sets. This will also tell you the suns position at each minute of the day. This is vitally important to get the right light.
I found the below video amazing in just picking up a few pointers. Helps that Michael is quite light hearted about it too
The Basics of Nature Photography by Michael Melford
There's loads of different sub genres to landscape. Waterscapes, cityscapes, long exposures, hillwalking, mountainscapes, travel and many more. It's good to find the one you really like, because you'll save yourself from a lot of sitting in front of a computer saying "It's just not right"
With regards to sharp front to back with the 24-105L I find that apertures between f/11 and f/16 are pretty good. Set your AF to about a third into the scene for general guidelines at first. The DOF preview button can help a wee bit.
Planning is totally key to getting it right. Watch the weather, the light via the app and sometimes even just call a business in the area to ask how the weather is lol.
Hope that helps.