Common mistakes/clarifications:

• First Aid Kits, Doctor Bags: Health, Downs, Custody, and You; (I've met so many Infamy ranked players who still don't fucking know this)
  
• Aced Combat Doctor (bad for reviving berserker builds and not helpful for DW)
• Aced Dominator (misleading description regarding power; only for civilians)
  
• Meatshield skills (and why taking only Basic Joker is not helpful)
  
• Bulletstorm (and why its niche and ultimately selfish)
  
• Oppressor (specifically how threat does and doesn't work, specifically on domination of enemies/civilians)
  
• Berserker (AND HOW IT DOESN'T MAKE SENSE WITH DODGE)
  
• Shotguns skills (and why Hardboiled is terrible both for shotguns and pointwise because Rifleman exists)
  
• Saw skills (and why Basic is all you need, especially with current mods)
  
• Silent Drilling (the pros and cons of having a loud drill in stealth heists)
  
• Sentries (which skills are actually useful but ultimately too much of a point investment as a deployable; extra points with Jack of All Trades)
  
• Dead Presidents (seriously, shoot me)
  
• ECMs (the pros and cons of having jammers)
  
• Silent Killer/The Professional (ultimately too much of a point investment to make silent weapons good; if they insist, I can point out a couple of good ok not terrible builds ~~because I hate myself)
  
• Leadership/The Professional (or any other percentage based skill that affect accuracy/stability; why the buffs are "fake" and not as good as cold hard cash stats/mods)
  
• Aced Thick Skin (IT ONLY AFFECTS BALLISTIC VESTS, NOT ICTV OR SUITS YOU GODDAM-)
  
• Swan Song (and why it's sometimes a clutch play and other times, a selfish godmode POS that I want to murder you for, especially when you mention Berserker)
  
• Dodge and concealment (and why a 10% dodge bonus is actually not really equal to 10% increase in survivability/durability)
  
• Armor vs. Dodge (pros, cons, why we don't use armors besides suit/LBV/CTV/ICTV)
  

/u/InterwebNinja made a really good guide for beginner builds here: http://www.reddit.com/r/paydaybuilds/comments/2m9azp/l0_build_guide_for_newer_noninfamy_players/

I nitpick on a couple of his build choices but overall, it's a good base to start from, especially at no infamy.