There are lots of methods of smoking ribs but I suggest following this the first time or two that way you will have very edible ribs that are fall of the bone tender. After your comfortable with the process then you can play with the numbers to get them the way you like them the best. You can also play with different methods and again figure what works best for you. Ribs is one of the very few things we smoke by time and not internal temps because it can be difficult to probe the ribs without getting to close to bone or to near the surface and getting a false reading.
If doing regular spare ribs you use 3-2-1 with a smoker temp of 225 degrees. Put the rub on the ribs (some do this the night before and wrap in saran wrap then apply a little more before going on the smoker) and put them on the grate and close the smoker. After 3 hours take the ribs out and put them in aluminum foil add a little liquid such as apple juice, or dr pepper, or honey, or about any other liquid then seal the foil tight and back on the grate close the smoker. After 2 hours take the ribs out of the foil and place them back on the grate and close the smoker ( be careful the ribs will have liquid in the foil and will want to fall apart they will stiffen a bit while back in the smoker for the finish) After 1 hour take the ribs out and shut off the smoker your done
Depending on type of ribs your looking at a 5-6 hour smoke you might consider doing something like a fatty, or hamburgers, or chicken parts, or abt's or the bacon wrapped onion rings Smokin Peachey just posted as snacks while waiting on the ribs to finish.
close the smoker then after an hour take the ribs out and shut the smoker down your done.
If doing baby back ribs it's the same method only the times change to 2-2-1
I usually serve sauce on the side but sometimes will baste the ribs during the last half hour of the cook the reason for waiting till the end is that most sauces have high sugar content that tends to burn pretty easy waiting till the last half hour lessons the chancesof it burning.