What kind of rig (short wheel base stick, dual axle bucket or TDA) are you looking at and what kind of structures and problem areas are you working on? The training, ops and use can be pulled from another Departments like yours (there is a ton on this site), but specing and buying are very dependent on where you can get service and support, or should be.
Any info would help.
-You first need to identify your community needs/resources and limitations, specifically you need to know the stations limitations that will house the rig. Height of overhead doors, length of the bay and gross weight supported by the bay floor.
-Next, what are the limitations of the community? Bridges, train trestles, street limitations, etc. Most departments are easily taken in with gigantic rigs that have huge aerial devices that far exceed their community needs.
-Having been on several committees that spec out ladder trucks I will offer this advice; short wheel base and a short chassis. Avoid the "gadget" mentality and things like "crab crawl or all steer", you'll be sorry in the end if you purchase these "boutique" items. Remember, most major urban departments operate 75' aerial ladders and 100' tower ladders. There are to many communities that have purchased 135' "sky arms" when the largest structure in town is a 3 story building.
-Stay with an American company that can get replacement parts to you asap, not coming from around the world. Or better still, a company that doesn't use "proprietary" parts. You want to be able to get parts at the local shop.
-A personal preference is Seagrave and Sutphen, Pierce is just not what it once was since it became a publicly traded company... and they use all kinds of proprietary stuff that must be purchased only from them. The two aforementioned companies are smaller and place a heavy emphasis on customer service.
-If you need more specifics with apparatus design please drop me a line. My colleges and I specialize in this matter as well as providing the entire training program including driving and operating the apparatus and the functions, SOP's and entire operation of the assigned personnel, including HOT training.