Ok, I guess this has been told many times, but I can't read all the topics here so I apologize in advance if this has been said. I don't take any credit or say that I am first or only one to know this, but this is what helped me the most and it's pretty basic.
Also, this is for people who are not rich as hell or already geared past act 1. If you are, you live in different world and this thread is not for you.

Buy shield with over 3k absorb and about 20% block with either vit or all resist on it. Doesn't have to be rare, magic one will do, but it helps a lot, and they're pretty cheap so there's no excuse not to. I had shield with 14% block and some resist all / vit and some other minor stats that was magic, and I went to test with cheap shield with more block and absorb on block (didn't spend more than 50k on it) and it was better.

Good dps weapon. I had 500 dps weapon with about 600 life on hit and I thought it was good, making me survive more. This turned out to be false, at least for me. I bought magic axe with 800 dps from AH (This was a bit more than shield tho, 350k) and my performance improved drastically.

Don't kite to entrances like most people say. I read and tried, and it's not like that. Find a room where you can move freely, that is clear of mobs and fight there (make sure that it's still enough close to checkpoint so they don't heal if you die, and you most probably will.

Do not release if your war cry with impurity is on cooldown. I cannot tell you how many times I get them to low hp, die because I get vortexed intro center of arcane circle and release to finish them off fast, not realizing my shout is on cd then got oneshot. Make sure that it's off cd so you can reuse immediately.

Minimize the amount of hesitation. I had this problem all the time at start, not knowing whether it's good moment to go or not, so I just end up going back and forth getting hit like a dummy. Pick the perfect moment to go in, preferably with all cd's up so you can maximize the damage output before you have to run out to avoid dying.

Inspiring presence. Ok, so we have to run 2 passives for armor most of the time, third is optional in all builds, at least that's what I see around here. I use this one because regeneration gives me edge when kiting to get my cd's back up, and most importantly I don't have to pot while kiting uniques to open zones near entrances, saving pot for when I charge in.

Hope that helped at least a little, I'll add more if I remember, but these got me from maghda to Belial today, so I thought you'd share.
Much love for Barbarians :*