By "Restricted's" are you refering to military rifles, or pistols? The fundamentals of shooting don't really change regardless of firearm classification, only the techniques used for each type of gun.
The principles of good marksmanship are holding, aiming, trigger control, breathing and follow-through. I can't type enough here to give you an intro to everything, but Google is your friend.
I always suggest a newbie begins shooting in the most stable positions and progress to the least stable postions as thier skill improves. The best starters for rifles are prone supported, and sitting at a bench. You can use a simple backpack or sandbag as your support, or a bipod or fancy bench rest if you have one. For handguns, there are a couple of different techniques for gripping the firearm, and your hand shape and body type may dictate which one works bext for you. Try You Tube, and see some of the instructional videos from the pro's. The give a few positions a try and see which one performs best for you. With handguns, you can shoot supported as well to reduce the number of variable you are focusing on.
The rifle positions allow you to focus on the fundamentals of solid aiming, trigger control, and breathing. After you feel comfortable with the core elements, remove the rests and shoot off your elbows or freehand to increase the challenge. Once you have the basics down and understand how your grip, breathing, and trigger control affect your bullet placement, you can move on to more advanced positions like sitting (unsupported), kneeling, and standing.
Start with a small caliber, non-magnum, so you can practice on the cheap. I like to teach with open sights first, so you don't get distracted by too many variables. Start at close ranges like 50 yards, then 100 (or for handguns, 10 and then 15+). Eventually you will begin to show some solid consistency, and you can begin to increase those distances.
Only after you can produce very consistent performance at short to medium ranges should you start to look at your equipment to fine tune your performance. Steps like tuning your rifle or handgun, trying different sighting systems, experimenting with different factory ammunition, or handloading for extreme performance. Remember, a bad workman always blames his tools. A good shooter can impress you with a rusty old .22, just as effectively as a shiny new Steyr.
