My two-pennorth to add to the above, so you get several perspectives. I’ll answer from the point of view of what I do:
What do you take with you apart from the obvious, sleeping bag, pillow, washing gear?
One thing that I’m not into is “camping”. I’m generally out Monday through Friday, and I have the same wagon all the time.
On that basis, the first thing I would do is forget about doss bags and take a proper quilt. I do take a bag as well, but it serves mainly as a nice thick bottom sheet - the only time I would consider getting in it is if my night heater packed up in the middle of winter, and I can’t remember the last time that happened.
Wash kit needs to be in a holdall/sports bag which is big enough for all your toileteries, a towel, and a change of clothes. That way you can just grab it and run when the opportunity arises. I also carry the means to strip wash in the wagon and do that more often than not, simply because the way we work and the dirth of hygenic and working women’s showers makes that easier for me most of the time - plus I like to get into bed clean.
I self-cater, so I also have a stove, pans, cutlery etc. plus a selection of canned, dried and fresh foods. My truck has a built in fridge but that’s unusual, so if you want to go this way in the longer term a fridge or decent cooler is a must buy these days, although I confess to having managed without one for years before I got this cab.
I carry a kettle, stacks of kitchen towels and babywipes, clothing for a week and a cloth laundry bag which gets hung up under the bunk, water supplies, a bloody great box full of A-Zs of the entire country, spare tachos/defect books/ collection notes/seals/etc, a pair of flip flops to slip on when I get out of the truck at night or go to have a shower (verruca avoidance tactic), some big cushions to make the place homely, and various bits of PPE/wet weather gear.
By being self sufficient like this, I a) don’t have to worry about where I end up stopping, as I always have everything I need; b) have a comfortable home in which to spend what is, after all, the vast majority of my time and c) end up in profit on my night out money.
Now granted, this lot takes up a lot of room, and I have a space cab to fit it in…but I carried exactly the same kit when I had a tiny old fashioned low-roofed cab, I was just a bit more inventive about how it got stashed. The point is, it can be done. 
Do you look for a place to stop before you leave or do you wander around looking when you get there?
The nature of my work is such that I never know where I’m going to end up at the beginning of any given day…so I can’t start thinking about it until the last couple of hours. I tend not to use truckstops and MSAs because I feel safer out of them, although I will if there’s genuinely nowhere else, or if an area is known to be dodgy. We get our parking costs refunded, so that isn’t an issue.
Over the years I’ve developed a mental list of my favourite “hidey holes” so will try and head for one of those - industrial estates are generally a good choice, as they’re well lit, free, and if you can get near a place which works through the night (parcel depots are usually a good bet - in an unfamiliar area, follow that Tuffnel’s van!) they will generally let you use their toilets/kettle/washrooms etc if you ask them nicely enough. Use a spot regularly and they’ll get to know you.
I’ll also park on regular customers’ premises where I can, and again, if they get to know you and you’re always polite and leave the place as you found it, they’ll often let you park there if you’re passing, even if you’re not actually loading or tipping there - we have one customer which regularly has several of our wagons behind it even when their job isn’t on!
I do laybys as well, although I aim for the ones with a decent gap between you and the road, and have got to know what time they are generally full by. Again, it’s incredible how you’ll get to see the same faces from all over the country in the good “spots” - there’s a whole sub-culture of us out there who swop tips on safe, quiet places, but we don’t tell just anyone…you’ll find that once you’re face get’s known you’ll be let in on those secrets if you choose to park this way. Again, it’s not for everyone - most of us are the self catering type with families to support - but there’s nothing better than pulling into a well hidden layby in the middle of nowhere and recognising the wagon in front which is based at the other end of the country from you, but which you parked next to three nights ago!
People complain that drivers’ cameraderie has gone, but this is where you’ll find it. The best way to get chatting is when you pull in behind someone who’s obviously still awake - bang on their door and check what time their leaving and that they have room to get out if it’s before you, and you’ll be treated with the respect you deserve for doing so. There’s nothing that irritates us regular layby monkeys more than a truckstop boy getting caught out and blocking you in because he didn’t think to check.
What time in the evening do you think about stopping?
We run our time out, so we’ll stop when either our 13 or 15 hours speadover is up, or we run out of driving. If we’re slack on work, it may well be when we can’t go any further until we’ve tipped out the following morning, or whatever.
Is it best to stop at a recognised service area or will a lay by do?
Horses for courses that one. I’m a layby and Industrial Estate monkey myself, and never pay unless forced - even though we can reclaim it. There are arguements on each side of this one, so stick with what makes you feel safest, unless your employer dictates otherwise.
If you find a place to stop say about 6pm, do you just sit in the cab until it’s time to go to bed (what do you do to while away the hours)?
I cook my dinner - unless I’ve run late and stopped to do it earlier, which I tend to do if I’m on a 9 hour break that night.
I then sit and read a book and/or listen to the radio (I’m a big Radio 4 fan in the evenings) for an hour or two, or lie in bed doing the same thing, until I’m ready to doze off. That can be a few minutes or a couple of hours later, depending on what sort of day I’ve had. Washing - either in the truck or whatever - takes up a bit of time too.
I do have a telly, but rarely bother watching it. Again, each to their own. Whatever you’d do at home, really, if you go equipped so you can.
Do you remove the tacho chart?
I pull mine at the end of the day, and write out the one for next morning ready (unless I’m going home and the wagon might get moved) so that I can just stick it in and go. I hate getting up even a minute before I have to. 
Can you go for a few pints, I’m thinking of the legal aspect, if you’ve had a drink and you go back to get your head down and the police want you to move the unit, say there was a fire close by?
I’m not really a drinker, so this one doesn’t affect me these days, but I know many do. Just be sensible about it - so long as you’ll be sober to drive when you need to next morning, you’ll be fine.
What time in the morning do you set off again?
Usually between 9 and 11 hours after I stopped, as either the job or the tacho hours I have left dictates. Obviously if I’m parked on a job, I start when they do.
Hope that gives you another view. 
While some do - obviously, you have to use your common sense about limits. A fire close by■■? You can’t plan for everything! 
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