I love spares, and hardly ever do babybacks.  The prep I use is to remove the membrane, slather in yellow mustard and my favorite rub, wrap in plastic in the fridge overnight to "get happy."  When they go in the smoker, I sprinkle on a little more rub, throw in about 2-3 oz of hickory/peach or hickory/cherry, set the temp to 225, and not mess with them for about 5/12 hours.  At that point, I'll take a peak for pullback on the bones, and see if they look done.  I always use a water pan full of apple juice on spares, and they come out very moist and tender.  No 2-2-1, 3-2-1, or anything....just let 'em ride!  These smokers really do make some great "Lazy Q!"