Welcome aboard! It's good to see younger folks interested in BBQ. The search function will get you where you need to be, but in the meantime a good basic rub is 3 parts brown sugar, 1 part each salt, pepper, onion powder, garlic powder and paprika. If you're smoking above 225˚ use Turbinado or natural sugar (brand name is Sugar in the Raw), as it's less likely to scorch and turn black. For your first time out though, stick to 225˚. It'll take a long time, but it's worth the wait.
For internal temperature, let it go until 160˚ before you wrap it, should take around 4 hours or more. Once you wrap it in foil, let the internal temperature get to 200˚ or so, or until you can stick a knife or skewer into the meat with little or no resistance. If it has a bone, the bone should pull free easily when it's "done".
By the way, when you wrap it, add a 50/50 mixture of apple juice and apple cider vinegar to the foil. You'll want about a cup total. Just leave one end open and pour it in.
Now, since you're new to this, I'm gonna bore you with the second most important thing. KEEP YOUR HANDS AND WORK AREA CLEAN CLEAN CLEAN, and make sure your meat stays BELOW 40˚ until you're ready to pull it out of the fridge and put it in the smoker.
What's the MOST important part? Have fun.