Need a little help with nightmare
Okay so I used to play Diablo 2 a lot back when it first came out....however I pretty much just beat the game on Normal with each class, and lost interest in Nightmare. I just beat Baal on my Warlock, and am wanting to get to hell...but idk shit about anything passed normal mode. So far I have just made the Leaf, and Stealth runewords and breezed through Normal with random other gear. I am level 33, pretty much all my skill points have been dumped into Ring Of Fire, Flame Wave, and Apocalypse, and I am wanting some advice on what I should be doing before heading to nightmare. Should I do the Cow Level? Should I use my respec and switch things up? Should I farm runes? Any specific gear I should snag before heading into Nighmare? Pretty much all I know about Nightmare is enemies have alot more resistance to things, and i need to have alot more resistance to things.