How do we make decisions? There's no right way: we could flip a coin. The "proper" answer is to make a list of all the pros and cons, weight those by utility, and pick the option with the highest utility. Then there's the one about taking the first option that's better than the first one you thought of - though that really applies to temporal processes like job offers and picking spouses. Some people who commit the sin of linguistic inflation call these "heuristics", though more homely terms are "rules of thumb" or "guidelines".
These rules and guidelines assume many things, one of which is that the decision is really about what we think the decision is about. Here's an example of when it isn't.
Renewing the mobile phone contract sets my inner "proper" decision-maker up for the long haul. It triggers my inner scrooge and it also sets off my inner little-boy-who-likes-toys. My inner Scrooge thinks it's a huge waste of money to be on a monthly contract with 300 minutes when I barely make any calls. Or even receive any. My Scrooge accepts that one decent job offer justifies a good few years of minimum-cost mobile ownership, but that's as far as it goes. As for iPhones, mobile internet and the rest, Scrooge is having nothing of it. Meanwhile, in my left ear my Inner Boy is whispering that if I don't get a fun phone this time around, I'll spend another two years regretting the decision every time someone does something cool on their HTC or iPhone. The last time I went through this process I was comparing the iPhone (horribly expensive) vs other phones that weren't really comparable but were almost as expensive, or free phones that had the core functionality but not the pizzazz. This time HTC are producing phones that have near-iPhone functionality and good, anonymous styling.I like anonymous styling; it doesn't say anything about you, and it doesn't attract thieves.
So I set off on a long cost-comparison exercise, complete with calculations of break-even minutes / month - which at 25p per minute on a PAYG contract aren't many - after taking into account data contracts and the like. Half-way through this, after putting together combinations of low-function PAYG phones and schlepping a £100 slim camera and my Nano everywhere, I suddenly wrote down what I wanted if I didn't give a damn about cost. Which was: a DSLR camera, a Macbook Air and a 5MP smartphone, most likely the Desire S, on the cheapest contract that made it free.
Which changed the nature of the decision. It wasn't just about the phone, it was about my personal, portable electronics. I have been finding my trusty Canon AS510 a little restrictive of late. What I was looking at was an upgrade. I did that with my TV and hi-fi a couple of years ago.
This is one of the many things that's wrong with the classical theory of decision-making: it assumes that you know what the decision is about. Whereas often you only think you do. In some parts of business what I did is called things like "scope creep" and frowned upon. But sometimes what you really want to do isn't what you start off thinking you need to decide. You might be thinking about which movie you want to see, but really all you want is to get out of the house and do something, anything, for a couple of hours. If you persist in seeing the decision as being about movies, you won't do what you really want to do, which is not-be-in-the-house.
Having decided that this was about upgrading, I could dump the Scrooge options and stop attempting to justify an HTC smartphone. An iPhone would need justification, because it's so much more expensive than the almost-comparable (for my purposes, maybe not yours) HTC's. The Desire S on the cheapest contract that makes it free, along with the company discount, now becomes a shoo-in.
Now I could look for a DSLR. Since I work with a qualified (and very good, IMHO) wedding photographer, I asked him about cameras. For what I wanted to do, he said, I should get a mid-range (£400) consumer model and spend the money I saved over the next-up (£700) on a decent lens later. Which advice and some reading got me to the Canon 1100D. What Camera? liked it, Amazon reviewers liked theirs, I like the pictures my AS510 takes and I don't see myself with a Nikon.
I need internet access and portable computing, since The Bank doesn't let us access our webmails and its internet access is a frustrating exerience (it still uses IE7!). I don't need that every day, but I should use it more often than I do. I have an Asus netbook (running Ubuntu Zonked Zebra - I'm cool) already. It's anonymous, already paid for and slightly heavier than the Macbook Air. I do notice its weight in my Eastpak messenger bag (Eastpak messenger bags are the epitome of "anonymous style"), but while the Air isn't that much lighter it is way, way more expensive. There's the iPad, of course, but it has no real keyboard. It's for media consumers, and I'm a text producer.
Accepting that this was a decision about upgrading also changes the conversation with my inner Scrooge. I'm not now arguing about the details of various money-saving schemes and the relative value-for-money of the options. Details are how Scrooge distracts me from what the decision is really about. He knew he had no chance once I made it about quality-of-life. I'm not going out and splurging on a £1,000 DLSR, a £45pcm iPhone contract and a 128GB Macbook Air. The Air is on hold indefinitely, as it breaks the "anonymous" part of my chosen mode of "anonymous style". That's also why I can say NO to the iPhone.
Sometimes you make a decision by making another, larger, decision which is easier to make. I could quibble with my inner Scrooge about how many minutes of calls I expect to make for hours, but he's going to have a hard time telling me that I haven't felt the urge to upgrade my kit for a while now.
Here's a very important rule about decision-making. Money should never be the deciding factor. What you can afford sets the limits, but within those limits you decide what fits your style best. And if nothing does, either don't do it at all, or take the cheapest option with the least commitment. That way you can get what you want later, when you do have the money, with the least wasted spending.