I've spent some time recently figuring out a suggested plan of action for those just starting Parkour or considering beginning. This is what I've concluded. 

First off, do some research on your local scene. If there is a group running classes, consider yourself lucky - classes are still growing globally and are still a long way off access for all. Get yourself along to a class (preferably indoor to start) to learn from those more experienced than yourself. This is a good basis to have throughout your Parkour training so keep in touch and train with more experienced Traceurs when you can. If there are no classes nearby find a training partner or group of Traceurs who already train regularly. PKGen’s community section here may be of use.

Learn the basic movements - vaults, rolls, a bit of climbing and some balance work. Repetition is key – drilling a movement will solidify it in your muscle memory. At the same time, work your body hard. Conditioning will make you more capable and will give you 'body armour' to protect you should you make a mistake. Condition regularly. 

Start small, think big. Take on jumps or movements that challenge you but you can complete with good form. Once you can nail it every time, move to a similar but larger jump. Link movements together regularly to form routes so you become used to moving through your environment.

Start training outside as soon as possible. Learning indoors is a great way to attain movements you want in a safe environment but it only really serves as a precursor to outdoor training. Be safe – outdoors is a totally different terrain and is a lot less forgiving than the indoor environment. Again, start small and familiarise yourself with small movements, various terrains and different feels of different surfaces.

Observe. Watch others both in real life and on YouTube. Get inspired by their movement and don't be afraid to try new things or challenges. You can even observe yourself - video your movements so you can see what they look like and what you may need to change. 

Finally, once you start progressing, train, stretch and condition regularly. Eat healthily and well. Continue to try new things. Particularly those that you hate - never neglect anything. 

And most of all have fun!