I started in the library world a few years back. This is starting my fourth year. I have learned a lot in that time regarding collection development. My predecessor used a lot of subscription programs and companies to order her titles, she used online stores and ordered off and on. I decided to change a lot of that when I took over the library. Here is the method to my madness:
First of all, I delve into my Kirkus review each and every month. I have a collection development spreadsheet and a Wunderlist for collection development open and I jot down notes (The Wunderlist is a task manager where I put the pub date. I get a notification of when it is due out.), a wishlist, and the genre the fiction title fits into. I look through my Kirkus to find titles that kids in my school would enjoy. If I have a few kids who read a lot, I will ask them to peruse the book review and get their thoughts. More often than not, we are on the same page. I spend time each month doing this. I also look at my ILL list and see what I have requested from ILL often. If I notice a pattern, I add that to my Nonfiction wishlist. My aid and I keep a series binder that we update with new series titles. We rely heavily on Goodreads as well.
Secondly, I attend the free webinars many publishers offer each month. Some of the best books I get come from hearing about them at these webinars. I use my Wunderlist and Collection Development spreadsheet and type away as the publishers talk. I also attend the Nonfiction webinars too, because often, there are a few great titles that pop up there too.
After I spend time doing these things, I start shopping. I get my budget in February, so I spend most of the spring and summer working on this. I have a local Indie store that does most of my new title ordering. I find the actual price and she offers me a 30% discount. It is usually cheaper through her than amazon. I am very tight with my budget. I am not afraid to buy used books. I go to a site a came across a few years back- Thriftbooks . Shipping is free and they offer used books that range from Like New to acceptable. We tried acceptable one time and were not pleased with the quality, so I stick with Like New and Very Good. I have built my collection dramatically through using used stores. In a school of 225, who cares! The kids will read it. The trick with used books, you have to make sure you don't have it already- so I always cross check in the collection to make sure I don't duplicate. I tend to order my Nonfiction titles through Thriftbooks because a lot of the Nonfiction books out there generally cost a lot more new than a fiction title.
If I go to a book store, such as Half Price or to a book sale at a public library, I always have my handy Destiny App available. I will spend hours looking at titles and cross checking for duplicates.
I pride myself in collection development. I love to research and study my needs. I have managed to change the annual order of about 100 books to almost 400 just by being frugal, organized and willing to go used. It has helped my kids grow as readers and find new things to appreciate and enjoy.