I am with the others. They just call to me. I will stand there and look at every betta. I will set aside the ones I like, and then when I look at them I just feel I know who I am going to get. I will often decide which tail type I am after that day and what main colors I want, but if someone yells at me to get them I have to.
Just the other day I went in to get my other red VT to be a twin to one of my guys. I picked him up, but while I was there I say this extreme multicolor VT with some curl fin... I just knew I was going to get him, I knew that day before I set out that I would end up with another. I wasn't planing on it but I knew I would.
So I guess it boils down to a mix, I know what I am looking for, I look for the healthiest guy who is flaring and seems happy and healthy, but I get the one who calls out to me the most.