I don't have a particular process, and don't really consider myself a collector in that way. If I like the watch, and I think I'll like it for a while, I get it. For me it doesn't need to be any more complex than that.
Over the years I've noticed a couple of things that happen with people...nothing scientific by any means, just my casual observations, and these are also from non-collectors.
Your tastes will change. Mine certainly have, and a lot of the watches I used to really want, I look at now and wonder what I was thinking. I have seen people make very dramatic shifts in what they collect, sometimes with those shifts coming full circle and people collecting again what they did many years prior. A personal example for me is the Speedmaster - I used to look at them and think "Meh - what is all the fuss about?" but now it's the watch I wear the most out of my small collection.
People burn out in this "hobby". I find that those who are chronic flippers of new watches in particular, tend to burn out quicker than those who are a bit more measured in their approach. I've seen people who flip easily 100+ watches a year, and they don't tend to be around for too long. There are certainly vintage collectors who are constantly dealing and trading, but that's different. I'm talking more about the newer person who goes all in, and "tries everything they can" in a short time.
My buying is not really impulsive. I buy watches with the intent to keep them, so I take time to carefully consider if it's a watch that I think I'll keep. I take even more time before I decide to sell. This is why I've never had any regrets about what I have sold, and haven't ended up buying the same watch over and over again as I've seen some others do.
Cheers, Al