What do you wish you had known as a new player?

As many have said: use a buildplanner to guide your progress through the skilltree. To expand on that, i use the following guidelines for progress.

- I take all damage nodes while I am in Normal difficulty. This is roughly my first 40 pts. Alternately I seek to get my major offensive keystones by the end of normal.
- I take all defence nodes while I am in Cruel difficulty. This is roughly points 41-71.
- In Merciless I keep doing the defensive nodes and niche offensive skills, and get my keystone defensive nodes (Mind over Matter, Chaos Innoc, etc). I usually get up to 85pts before mapping and 105pts by the time i considered a character "done"

Start off as life-based or ES/Life. If life based, shoot for about 180% increased life. If hybrid ES/Life then shoot for about 125% increased life and 125% increased ES. Choose the right equipment to support this. Try to get all resists to 75% - chaos will be hard to do.

Try to get 2 layers of defense, majoring in one, and minoring in the other amongst these: blocking, evasion, armour, life/ES leech, movement speed, dodge, specialty keystones, or equipment based 'tricks'

As you design consider if you want to leverage a character's ascendancy abilibites, a certain combination of unique items, or active skills.

You can have 5 or 6 items with slots depending on whether you use a 2H weapon, i usually split the skills in these items up like so:
1) Single Target Damage (5 to 6 links)
2) AOE Damage (some skills can do 1 and 2 at the same time)(4-6 links)
3) Enemy Debuffs (curses for example) (3-4L)
4) Player Buffs (Auras for example) (3-4L)
5) Movement Skill (4L)
6) Utility Skill (totem, minion, golem, etc)(3-4L)

Random thoughts:
- your flasks are important, roll them well and keep them updated
- your first few builds will fail
- in normal and the first half of cruel, slots/links in gear are more important than stats
- skills have attribute requirements, if you try to mix pure STR and pure DEX and pure INT skills you might have to waste equipment affixes on stats or be forced to grab potentially inefficient skill nodes in the tree.