Converting from scrumhalf is, unfortunately, easier. But, I actually did play scrumhalf a few times when I was about 13/14, so I don't really remember that much of the specifics per say, but I'll offer a few, admittedly poor tips. Also no matter what you will become some supporters pet hate, if you get slow crappy ball and then take a few seconds to organize your forwards- you can't deliver quick ball and are subsequently useless; if you fling it out in a manicly thus delivering said quick ball it will put and unorganized attack under pressure. Be warned!!!
First: You've got to be able to pass, pass, pass, and pass again, consistently off both sides. Your passing should be around chest high, and also varied, don't just give it to the outhalf, pops to forwards, switching sides every now and then, allow pick and go's, run it out from the ruck and then pass, it doesn't just have to be a static pass all the time- I know from my first few games there that it was daunting as f**k to attempt anything else, but don't be afraid to try and mix and match a bit. Check youtube for videos of drills, but most importantly don't try and force yourself into passing in a way that makes you feel too uncomfortable- you'll end up thinking about it too much! Instead what I found very helpful in developing my own pass was just to spin it up into the air, at varying heights and angles- it sounds stupid, but passing felt more natural to me after spending time doing it.
Check out videos of Peter Stringer- or just watch old Munster or Ireland videos, his pass was crisp, quick as hell, and he encouraged the player he was passing to to run onto the ball by placing it just in front of them. Seriously watch him and you'll learn a lot about proper positioning of the feet upon arrival at the ruck to ensure quick and clean delivery (your main aim!).
Second: Play to your strengths. Take for example Mike Phillips, not the greatest SH ever, but incredibly effective! As a winger you probably have decent pace, and are fairly handy at spotting and going through gaps, use this to your advantage and attack the fringes every now and then. It will keep the opposition defence guessing, and if done correctly, will take a lot of pressure of the rest of your team (esp. the outhalf). Don't overdo it though.
Third: Communication. Talk to your outhalf and forwards, if you want something to happen don't just expect it to tell your players what you want, but also just as importantly listen to your players if they tell you something (esp. your outhalf).
Fourth: Awareness. You need to be aware of where your players are and where the opposition players are. As well as being aware of what both your players and the oppositions can and can't do, if they have a full back or winger out of position for example, it might be a good time to chuck a kick his way. Also some players hate passes coming too quick at them if they have poor hands, although the best way around this is actually supplying a good pass in the first place.
Fifth: Just chuck it about with your mates, they will be more than able to tell you how crap everything your doing is and how you are making life difficult for them!
Mainly though watch videos on youtube of the likes of Stringer, Yachvili, Pichot, Du Preez- they have all played intelligently and would be a good place to start learning from. Also don't forget to listen to your teammates and coaches they will be able to analyze the way you are playing, and what can be done to improve upon this better than anybody else. Remeber though confidence is key, if you cock up at SH it is very easy to loose confidence and thus lessen your impact on the game vastly!
I hope this helps, I'm afraid I can't really go into any great tactical depth as I never really played there much.
