The first month or two after arriving will test your patience. You will be starting your training while at the same time dealing with all the administrative things such as getting your residency permit, driving license, company- and government medicals etc, in a never ending string of "character building" tasks.
To make your life simple, and avoid major frustrations, prepare the following before arriving:
Bring an international driving license and go online to book a rental car before you get here. It is absolutely necessary to have your own wheels as QR will only provide transportation for the first week.
If you plan to bring your family, get your marriage certificate, children's birth certificates and children's last two years' school reports certified by the Qatari Embassy in your home country. Contact the embassy directly for guidelines. You will need to have school reports certified by your Ministry of Education, and marriage/birth certificates certified by your Ministry of Foreign Affairs (or equivalent) before presenting them to the Qatari embassy for their chop. This is absolutely necessary in order to get your family's residency permit and school places. These documents then need to be translated into Arabic by a translation agency in Doha. Yep, really.
Get in touch with schools before you arrive and find out exactly what is needed in order to get a place. You will need to present all above mentioned documents to the Supreme Education Council in Doha for their approval for your child to start school.
QR will assist you in opening a bank account and will give you an advance of half a month's salary when you arrive. Until then all ATMs accept foreign bank cards for cash withdrawals.
Joining is a frustrating exercise of bureaucracy and QR can only do so much to assist you but once you are settled and everything is in place QR is a good job and Doha is a decent place to live if you keep your expectations realistic!