What tips should I consider when buying my first set of "real" golf clubs?

I’ve been playing golf casually, a few times a year, my whole life. I’ve been using the same $200 complete set I bought 15 years ago in high school. Now, I’m thinking of upgrading to a better-quality set from a well-known brand like Titleist, Callaway, or Taylormade. I have a few questions:

  1. Besides Craigslist and eBay, are there any other trustworthy websites where I can buy used clubs online?
  2. Can you recommend brands that offer good quality but are affordable? I’m not looking to spend a fortune.
  3. I’m 6’2" tall. Should I ideally get fitted for longer shafts?

I live in the Fairfax, Virginia / DC area. I’m not aiming to become a pro golfer; I just feel it’s time to upgrade from my old set from a big-box store.

Check out GlobalGolf, 2nd Swing, and Rock Bottom Golf for used clubs online. Brands like Cobra and Wilson offer good quality at affordable prices. At 6’2", a fitting for longer shafts is recommended.