I feel your anxiety. I purchased my first MH in June of last year and was really nervous. 36' was as much as I wanted to handle for my first coach but ended up with a sweet deal on a 38' Dutch Star DP. I was given one driving lesson that lasted all of about 15 minutes by the sales guy. Turns out that was all I needed. Here are the tips I received and have observed (some of which have already been mentioned in prior posts).
#1 Do your homework on the routes you intend to take. The less experienced of a motorhome driver you are, the more homework you might want to do before going on your trip. Have the passenger designated the co-pilot and that person is responsible for reminding the driver a couple of miles ahead of time that an exit is coming up in X miles. They can help in lane changes, watching for overhead branches, and being your backup eyes and ears.
#2 Mirrors are your newest, bestest friend. Check the top mirrors for traffic coming up on you and check the lower mirrors to see what is beside you. Watch those bottom mirrors regularly to gauge where you are relative to your lane and use them as you are turning to see how close you are to the curb when making turns. You will need to swing out and as you begin to make the turn the mirror will help you see if you are cutting it too tight.
#3 Backing up is tricky. See lesson #1 on home work to reduce the number of times you have to do #3. It is unavoidable and as others have suggested, work out a system with the co-pilot to be your spotter and help you do the backing.
#4 Do things well in advance and don't rush anything. If you have done the homework and you have a co-pilot, you should be able to change lanes in sufficient time whereas to not do anything in a rush. When changing lanes, hit the turn signal, check the top mirror, then the bottom, then the top, and then carefully watch the bottom as you begin to creep into the lane. Leave plenty of room in front of you and remember it will take you longer than you think to stop.
#5 Have a fear of snakes and have been told, "They are more afraid of you than you are of them, trust me"? Think of all the cars on the road as snakes. You are much bigger than everyone else and for the most part, people don't trust the drivers of rigs to know what they are doing so they will naturally be afraid of you. They will get out of your way if you give them the opportunity (see the note about doing things in advance and not rushing).
#6 When you are driving your car on the highway next, pay attention to where your eyes focus on the road. Your natural tendency will be to use that same distance when you first attempt to drive your rig. Don't. You will need to focus your horizon much farther out or else you will constantly be adjusting your steering and it will wear you out. If you focus farther down the road you will find you correct less and it is a wonderfully calming experience driving your rig. Also, new drivers tend to hug the right side of the lane. If you notice yourself doing it, just use those mirrors to learn how to drive the motorhome with equal distance on either side of the lines.
#7 Think of all the 18-wheelers, motorhome, campers, and slow moving construction vehicles that have slowed you down over the years as an automobile driver. It's YOUR turn to be that guy!! Never make a risky decision because you feel like you are slowing people down. If you wreck, think how many more people you will inconvenience. If you start to make a turn at a light and you realize you don't have the room. STOP. Don't force it. Let people back up, move around you, do whatever. Will they be irritated? Sure, so what. Take your time and make sure every move you make is the right one and if you aren't sure, do whatever is safest even if it means blocking traffic for a traffic light or two.
The tips to drive around a big parking lot is good as is getting up fairly early and getting the coach out on the road while the roads are mostly vacant. I was told it takes about 500 miles of driving before you really start to feel like it is second nature and form motorhome driving habits. That was pretty accurate for me.
Good luck, be safe, and have fun.