Gear Ratios is the classic "how long is a piece of string" question.
I prefer a compact chainset, 50-34 on the front and a 12-27 cassette on the back. This gives me a great spinning gear, flicking betwen the 23, 25, and the 27 on the back depending on the gradient. Triples are good offering good bale out gears when the going gets really tough but I find the middle ring is usually a 42 and not much use on the hill so it tends to be the Granny Ring all the way from St Esteve. The standard double set up of 53/52 - 39 is fine if you are feeling fit and are a natural climber.
You will hear horror stories about the weather conditions on the Ventoux, notably the 2000 Etape du tour which was cut short because of cold and hypothermic riders collapsing after Chalet Reynard. Indeed I have seen people blown off the tarmac and onto the rocks at the side of the road on more than one occasion. However, these conditions are rare and not the norm like most people will have you believe. The same can be said of the heat. This year in July 35 degrees was not uncommon in the forest. This can easily be avoided by an early start. Simple, get to Bedoin for 8am and you'll be fine.
If you are riding into the red during the first 30 minutes of the climb the chances are you'll blow well before the top. Remember the Golden Rule is not to jump on a wheel. You will pass people and people will pass you.
Ride at your own pace!
Breaking the ascent into stages is also a good idea. There are three distinct sections on the climb out of Bedoin.
The first 5.5km average just 4%.
The section from St Esteve to Chalet Reynard is the infamous climb through the forest, 9.5km of 8, 9 & 10%.
The last 6km are easier and psychologically when you reach the cafe you have broken the back of the climb. Remember though that the last 1.5km after the Simpson Memorial kick back up to 10%.