Depends really on how you feel and what you've been training, as all of us train differently. If you're very sore I hear that a day of rest + stretching + very light conditioning helps it heal fastest. The general rule is to listen to your body though; if it hurts a lot, stop. Try to be more specific though; your question is pretty broad.
As Fyrel says, "a day of parkour" means something VERY different to different people.
Even beginners to the discipline can come with VERY different backgrounds, physical conditions, age, training experience, tolerance for discomfort, and understanding of body signals.
a.) "if aches and pains are minor, they are simply indications that muscles are adapting to your new exercising program, and mild soreness comes with any kind of physical activity, especially when beginning a new type training.
In general, if you're not sore to the touch and you have your full range of motion, a light activity will stimulate blood circulation to the muscles favoring recovery"
Until you don't feel like you can reasonably train safely again?
There's no rule of thumb... a day break (48 hours after the previous training) may be a good idea; 24 hours is a standard, but it's arbitrary too.
I did 3 days like that back-to-back 2 weeks ago, but I've been training Parkour for 3 years and been physically active without major interruptions all my (long) life...
Nevertheless I was drained for the whole week after.
You really need to figure out this yourself with (cautious!) trials and errors.
Hope this helps.