What does everyone use for their center serving material. Halo was recommended to me. I was thinking about buying the tools and replacing my own. Any advice would be appreciated.

I use #62....no problems yet.

Never used halo before, so I can't comment. I just use braided nylon. I usually stay away from mono. Size of the thread depends on string thickness and arrow nock size. Once you get the hang of it, it is vey easy to make your own center servings.