What should we consider the "standard"? Meaning, what do we say to new players? "Don't go beyond perking 4 skills!"?

I would also like to know, there seem to be so many perks and I want it in 1 handed, blocking, speech, heavy armour and restoration.

For the record I'm thinking 4... Maybe a sprinkle in a 5th...

Maximum level is 80, isn't it? With 15-20 perks per skill tree, this would mean 4-5 trees. However, you do not need to pick 'every' perk in a tree. For example, a sword using warrior would have little use for the axe and mace branches of the One-Handed tree, or a magician for the Fire / Frost / Lighting weapon damage branches in the enchanting tree, unless they feel like decking out their companion. For the record, I hope the DLCs raise the level cap by 5 level each like they did for New Vegas. This would be neat and allow for a broader selection of talents, because now that I look back on it for this post, choosing to maximise only 4-5 trees out of everything seems relatively restrictive, especially considering you might have made unoptimized choices in the earlier levels.

4-5, just like the NPCs. Although the NPCs and companions that are "Archers" use six.

There actually is no hard cap on levels, it is purely a mathematical level cap, based on how many levels you can gain from raising your skills.

I made some poor choices in the beginning of the game, not really thinking about my skill trees. I invested in 8 different skills, and am lvl 42.