The hardest thing to master on any new smoker is the temperature control. Keeping the temperature low and even takes time and you will need to experiment to get used to the idiosyncrasies of your particular smoker.
Take Chef Willie's advice about starting with chicken quarters but make sure you have a good digital temperature gauge so that you know what your smoker is doing and also the temperature of the meat.
Don't then try to hit the briskets straight away - try something like a loin of pork. This will taste good if you manage to cook it low and slow but will also taste good roasted fast too - if your temperature control still needs some work. After that the world will be your oyster...
Whichever you try first it is always worth trying out a few rubs - even on the chicken quarters. Start simple with just salt and pepper then progress to one from here that takes your fancy. You could even buy a commercial rub to begin with however these often tend to be high in salt and sugar.
One of the most important things - Don't forget to take photos to post on here