What is the best way to check for authenticity?

Thanks
V
OUT

Most fakes are pretty obvious to someone who has a lot of time around the real version.
I've rarely seen a fake that stood up to more than a cursory "hands on" inspection. Even the really good fakes always fail a good movement and timegrapher inspection.

If you're not intimately familiar with the watch/brand in question take it to an experienced watchmaker or to an authorized dealer who has a brand certified watchmaker on site and they'll let you know if it's real or fake.

This.

A real watchmaker, not the guy in the mall.

On a Rolex if you look at the dial with a jewelers loupe, everything will be perfect.
Every letter will have sharp edges, the letter spacing will be exact, the paint will be perfectly even.
The indices will be perfectly aligned and spaced, the lume will be perfectly applied.
The hands will again be perfect with perfectly applied lume and will hit every single marker dead on.
The date will be centered perfectly in the cyclops and every single number will be painted perfectly.
If there is a single defect on the dial it's probably a fake.

That's just the dial.
The case, bracelet and movement will all be as close to perfect as possible as well.

Rolex has such high standards and multiple quality control checks with basically zero tolerance for defects that it's extremely rare for any obvious defect to make it out the door.
Any visible defect would immediately make me very leery of authenticity.

Buy from a reputable second hand dealer like DavidSW of orlando

That sounds a bit like a Grand Seiko.

Yes.
Some brands just do not compromise when it comes to "perfection" and have prices that reflect those added man hours to achieve.
The reason a Grand Seiko SBGH001cost $5500 and a Seiko Presage SARX033 (which is a beautifully finished watch) sells for $850 is the attention to detail that requires hand fitting and multiple quality control steps.
The fact that you can only see many of those details with a 20x loupe is beside the point.

Post it on Rolexforum and ask if it's legit.

But the above poster's correct, most can be discerned in a matter of seconds to a half trained eye.

I've even seen quite a few arfcommers sporting fakes.

10 things to look for to see if its fake. (just went through this with my recent purchase)

1) if they won't open up the case back and confirm the movement, walk away. Period. Full stop.
2) For a rolex with the date window, is it lined up perfectly and do all the numbers show EXACTLY in the center?
3) "cyclops" on the date window needs to have that "black hole" effect when you stare at it. If not, the AR coating is not there or its not  2.5x magnifier
4) if it came with the original band, the links should be solid and no flaws as well as fitted PERFECTLY to the case
5) crown guards around the crown should be even and not have any machining marks
6) when you unscrew the crown, it should have good resistance and the movement adjustement needs to be correct for the movement type [tons o youtube vids on what this looks like, each model is a bit different]
7) The rehault needs to be properly marked and not look "cheap", newer Rolex watches have PERFECT markings there
8) If it has a divers bezel or the GMT style bezel, the rolex crown and the 12'oclock and the zero on the bezel should line up PERFECTLY for midnight/noon
9) The beat should match the model... lots of fakes have cheaper movements that are not as smooth as the 28800 beats per hour on the newer movement
10) the hand on the dial should be in the correct order. A Rolex GMT fake is VERY easy to spot as hardly any of them get the order right with watch movement adjustments that work like a real one.

#1 way to avoid a fake it to go through an authorized broker/dealer as their name is on the line and rolex backs it up. There is insurance against fakes with these folks and you can take them to court and Rolex will ass pound them in the courts for you.

Vintage Rolexes tend to have really cheesy, cheap feeling bands and stamped clasps, modern Rolexes are a whole different story.

True dat.

The older "folded" ones are nice to look at, but, they suck shit as they rip the damn hair off your arms. Which is why I have a leaather or synth strap on my Seiko.