WILDing is very complex process and there is lot more to it than time of the attempt. As much as you don't want to spend too much time on it, I recommend you read some tutorials and familiarize yourself with the basics and also advanced details of the whole process.

I could tell you, that the best time is after at least 4.5 hrs of sleep, but if you don't know anything else about it, you will spend more time on trying than you would if you educated yourself.

Here are some great tutorials
WILD class
Dream Yoga