Did you just order a R1 or are you considering it, and are full of questions?
Ask away in this thread.
Thankfully many of us have already climbed up that hill of knowledge, and the path is much clearer now than a few years back, and I'll hope that many join in with their wisdom, experiences and advice.
First some general tips.
RED 101 hosts a couple of instructional videos.
You can download the R1 Operations guide to familiarize yourself with this beast.
A good book to get you started is RED: The Ultimate Guide to Using the Revolutionary Camera
Reduser Jay A. Kelly runs the Infotech Academy with many useful videos and more.
Reduser is full of information, but the search engine is crap. Use a customized google search (tinyurl.com/reduser) or simply enter "site:reduser.net" before your search term. That way you'll get better results.
When buying used, be wary of scammers. If an offer sounds too good to be true, it probably is.
The Red Centre (now simply called RC) is a great podcast around digital cinematography. If you listen to the earlier episodes, you will get lots of great R1 specific info.
What do you need?
Besides the Body, you'll need power, media, optics, monitoring and support.
Power: You can either use batteries or mains; For batteries most people use V-lock mounted batteries. RED makes the Bricks, but there are other 3rd party providers, such as IDX, Globalmediapro to name just two that spring to mind. The alternative to V-lock is Anton Bauer mount, or short AB. Just a different way of attaching the battery to the mount. Some prefer the AB's robustness, others like the V-lock's speed. The R1 is quite power hungry, so be sure to get pleny of Watthours. And don't forget the charger - there are single, sequential and parallel ones. Sequential charge one battery after the other, and while lighter and cheaper, might not be good for you if you need all batteries charged while you are sleeping. Some batteries do not transmit their charge status to the R1 - in which case you can still use them, you just won't get a warning when they come close to being empty. Be careful about buying used batteries, as you don't know how they've been handled, and how much life is left in them.
If you plan on travelling by plane, be aware at certain restrictions in regards to LiIon batteries.
When powering the camera by battery, you'll also need a battery plate that holds and connects the battery to the camera.
Media: The R1s nowadays come equipped with SSD ports, so that you can use any of REDs current media, from 48gig to 512gig. You will probably find the prices steep, but keep in mind that the media has undergone extensive test to ensure that you won't lose a frame in your most important shot. While no longer produced, you can still get 320gig and 640gig RED Drives. These allow for longer run times, but being spinning, are prone to dropouts when the camera is moving. There are 3rd party solutions that minimize those problems (or simply wrapping the drives in layers of cloth and gaffer tape).
You might also get hold of a used Compact Flash Card port for the R1 (as they originally shipped in), which allows you to use 4, 8 and 16gig CF cards. But only RED and certain types of Lexar 4gig and 8gig drives allow for full speed recording. Other makes will be limited to smaller speeds/sizes.
Also, have a good backup system in place. Ideally, you should have at least three copies of all your footage on at least two different types of media in at least two different geographic locations. The most used media for now is spinning disks and tape (LTO-3 and above).
Optics: The R1 comes standard with a PL mount, a very robust mount that has long been the standard for 35mm film production. Lenses tend to be expensive, and they are all manual. You can buy cheaper, older lenses, but of course the quality varies. Thankfully, there are options that allow you to use Nikon, Canon and other stills lenses. See here for an overview of options.
Monitoring: RED offers both a viewfinder and a LCD screen; you can run both at the same time, just be careful to plug each into the proper plug. It is also possible to drive 3rd party monitors/EVFs, but they won't give you the added functions that RED's solution have. That said, many have started by running a simple small LCD screen off the R1, and bought better solutions once they could afford it.
For sound monitoring, you'll just need a pair of good headphones. You can listen to all four channels simultaneously.
Support: While you can screw your tripod directly onto the R1, it is not ideal, as you most likely won't be able to balance it. RED includes a decent solution in their Base Production Pack.
Be sure to get a tripod and fluid head that can support a fitted out R1. A Manfrotto 501 won't do. There are plenty of older threads about this. Good heads and legs cost money.
Post
There are people on this board that are much more knowledgeable about the post workflow than me, so let me just say that processing the R3D files is much easier than some people would make you believe. All major editing systems now allow native editing of R3D raw footage. Most current computers will give you a decent performance, obviously you can boost these by having a powerful processor and a RED Rocket card. I can still use by 2008 Macbook Pro to work on my files. RED provides a great tool for working with your files, RED Cine-X Pro, at a highly affordable price.