I’m about 3/4 way through the theory questions(app), and a lot of things to learn, you will be very green at the start.
Breaking down in tunnels, heights, overhead cable, lights, widths, weights, breaking down in general, accidents, roundabouts, illegal immigrants, and loads more.
I would imagine roundabouts could be tricky and dangerous especially as you generally got to keep to the left even if going right.
So what’s a list of things you encounter regularly?
Why would you keep to the left to turn right?? Left lane for left and straight on, or otherwise instructed.
Generally, unless you’re over 16ft 6” you don’t need to worry about overhead items. Anything less has signs, but that still doesn’t stop bridge strikes.
Depends on what type of work you’re doing, as to the most common encounter. Although I suspect the general consensus for common encounter could be any of the following;
The pointy shoe wearing office inhabitants that have never driven an HGV telling you how to do the job.
The pointy shoe wearing h&s monkey, that’s never done a hard days graft in his life, and the hardest thing he has to contend with is that he needs to buy milk.
The gatehouse inhabitants that grunt shout and sweat before turning you away because you’re either early, on time or 10 seconds late.
mardybum:
Why would you keep to the left to turn right?? Left lane for left and straight on, or otherwise instructed.
Many roundabouts have two or more lanes marked for right turns and a LGV is expected to keep to the marked left one
Also many are so tight that it needs a LGV to keep more left than right on the approach to turn without mounting any part of it
Also many are so tight that it needs a LGV to keep more left than right on the approach to turn without mounting any part of it
Very true. But, just to confuse the issue a bit more, some roundabouts you approach more to the right than left to avoid the left kerb on the way into the roundabout. And this, dear listener, is why good instruction is vital to make sure you know the difference!
Good luck all,
Pete 
As a noob, here’s a few- in no particular order:
Your sat nav is only a guide. My 520 trucknav will ‘often’ try to send me somewhere I couldn’t fit my Charade in (but I do a LOT of new builds up the back end of nowhere). Your size/width capability comes only from experience (in the same vehicle).
Road markings can be a load of ■■■■. In general, follow the highway core. Going right? Right lane. Eyes on a swivel if you need to change lanes. If you miss your turning on a roundabout. GO AROUND.
Get a dash cam (if not fitted).
Get a truck nav. Keep it up to date. Sometimes your nav will delay your directions, particularly in up-built cities, like london. Slow down, let it, and you catch up.
Your driver colleagues are your friend. Be polite and humble and ask away. If you act like a know it all ■■■■ they’ll most likely as not leave you to your own failure.
Drive to your awareness limits. If you have to drive slow to negotiate obstacles, do so. ■■■■ everyone else’s agenda. I hate brat runs at 08:30. If you have PRIORITY let every ■■■■ get out of your way. If you have to shunt a 3 pointer on a highway, then do it. Keep your eyes out.
Get to a site/depot and READ the delivery/pickup instructions on the gate. (if they have 'em!). Some ■■■■■■ get really ■■■■■■ because they think you’re psychic and know what you should be doing.
I’ve got more but I’m going to bed.
ROG:
mardybum:
Why would you keep to the left to turn right?? Left lane for left and straight on, or otherwise instructed.Many roundabouts have two or more lanes marked for right turns and a LGV is expected to keep to the marked left one
Also many are so tight that it needs a LGV to keep more left than right on the approach to turn without mounting any part of it
Good to see what I replied with was read and processed before making a reply 
Flip flops have a nasty habit of sitting in the left lane with their right indicator going, in order to exit a roundabout on an exit past the 12o’clock position. 9 times in 10, Daisy on her way to work doesn’t understand this and a near miss or accident occurs. So again;
Left lane for left and straight on, or otherwise instructed.