I suppose a good way to go about this is to build elaborate, bending, stretchy, convoluted, intertwining, tiered, crunchy, complicated environments. Expand the vertical field with elements that compliment the environment from different angles. Seeing how different the environment looks when venturing to another side of a monument will beckon the act of exploring, and if there exists a path plethora, backtracking will not be so much that as it is adventuring- and if there must be a "locked door" situation, its a better idea to make it hold hands with the scenery than to plop an iron door.
I think player society could agree that a fire pit is more comforting than a padlock, a high cliff more endearing than a mahogany panel and a brass handle, and a tough cookie of a character looking you in the eye more of an important event than a cleverly disguised card key swipe.
I passed a locked door. God dammit.
I suppose a split path situation is best solved by destroying the act of backtracking or making it relatively painless. Allowing
multiple instances of subjective decision making in an alternatively rigid game play track tempts the player to return to an area. Forcing them to walk the trampled path is not a bad choice if they are aware of the options around them.
oh- my GOD! I can go IN the tree as well as AROUND it! Genius! Bloody genius!
Now, don't confuse amoeba like and placid environments as a million paths. The FF12 route does not entice exploration so much as it urges boredom.
<-- This game really neglected the Y axis... Not to mention the FUN axis.
There are a lot of complaints in the air about linearity, and personally, I don't think linear gameplay is all that crummy. Having a game go from level to level is a much better alternative than mindless backtracking. To make linear gameplay more exciting, there should be options about how the player can go about things. In Metal Gear Solid 4, there are a good 30 ways to go about each situation, so linearity and punishment are hardly an issue.
And now there's that damned key.
Now backtracking sucks, but as long as I have a way to find out where I'm going and there isn't a Cave Story Sand Zone effect going on, then I am perfectly happy to visit a land I've already trekked.