Hi Matt and Welcome to the group
There are a growing number of us on here from the UK - many born and bred here but some are also US exiles. Being in Lincoln you will not be far from another of our members - Danny - and he is originally from Texas. Some of us will be up your way in the summer for the UK SMF BBQ meet. We hold it in Woodhall Spa and it would be good if you could join us.
Congratulations on your WSM - they are great smokers. With a few hints and tips from people on here you will be on your way in no time. Remember though that there will be almost as many ways of producing the perfect smoked meat as there are members here. Although there is no single "right" way there are certainly wrong ways - and you will soon find out which works for you. Don't be hesitant in asking questions as that is the way we all learned, and don't restrict yourself to only hot smoking as the WSM will be great for some cold smoking too.
Now you have your smoker you should also invest in a good digital thermometer (e.g. the Maverick ET-732 or 733) as you will need to know the temperature of both your meat and your smoker at all times. You will soon learn to ignore the built in temperature gauge.
A pork shoulder will be a good place to start however before you do you need to master the temperature management within the smoker first. This will take several attempts and you may want to use something less expensive like chicken pieces or maybe a supermarket pork loin or even sausages. That way if all goes horribly wrong then it will not be too expensive while you are experimenting. Once you have the temperature control mastered then go for pork ribs or shoulder before you tackle your first brisket as they are much more forgiving.
The best place to get your meat is usually from a local butcher as most of the supermarkets are not geared up to supply what we want. Sometimes they do surprise you though. To begin with the US and UK cuts you will use will the same - pork shoulder is pork shoulder and brisket is brisket. If you can, get it unrolled - especially the brisket.
When converting US recipes though be careful if they use liquid measures as the US pint is 20% less than the UK pint.
We are here to help and we look forward to seeing photos of your first smoke