I've neglected Enchanting & Alchemy all this time. until I read your post yesterday I hadn't given them much thought. I usually put the first point into Speech, Alchemy, Enchanting, only because it's a 10% or 20% increase, but that's it. I'll be paying more attention to them now :]
I generally concentrate my characters. My first was a 2hand tank so I went deep into Heavy Armor and 2Hand, Block up to Deadly Bash (doesn't require a shield). My second was an Assasin so I went deep into Sneak & Illusion, some into Archery.
But I think I focus more on completing a story than building the character, none of my toons are over 40. When the quest lines I'm playing for that character run out, I start looking at starting another one. It's not the most efficient way to play, I know, but I guess it's a role playing thing. For example, the Listener of the Dark Brotherhood wouldn't go to Mage school, or be on the front lines of a war, that just wouldn't make sense from a story telling perspective. So I only do some quest lines for certain characters. My current guy is pretty general, so I think I might try to max him...who knows which direction I'll take him.