Lets see..tips...well you have already received some good advice but I'll add my 2 cents.
Practice. I'm not saying you need to go out and practice as each site is different so its just something you gather over time.
Good mirrors.
Take your time, regardless of people watching you. Even if holding up traffic for a minute. Happens everywhere, and everyone has to deal with it.
There is something about gripping the steering wheel at the bottom and turning the direction you wan the trailer to go..or something like that. Honestly, I never remember it, and I find it easier to just "figure it out" as I am doing it.
Have the DW only pay attention to one thing....whether or not your going to hit something with trailer or truck, or jackknife the truck into the trailer. Other than that, don't say anything at all.
That last part is my own personal mantra. I can see when I move the trailer the wrong way. I can see just about everything as I am doing it. I can't see things I might hit with the trailer or if its going to jackknife and cause damage. Actually with the backup cam I can see a lot of the possible jackknife..but not all. I also might not be paying attention to the vehicle.
Thats pretty much how I do it. It is 10 times more frustrating to hear "to your right...to your left...blah blah..other left...blah blah". I get it. I can see it. Just tell me if I am going to break something! lol