I think it's mostly a matter of self-control. Looking through my orders, there are some in there that were impulse buys, and I didn't absolutely need. Something like Chelsea? Absolutely must get. No regrets, there. But you need to find your own scale of what you can live without, versus the ones that are truly worth the money.
Words of the wise, my friend. That's the way I'll handle things in 2014.
I often-times, at least for 2013, hit the pre-order button on figures that I later thought "...eh, maybe I could do without it...", but since it's AmiAmi, I didn't want to cancel and risk the cancellation of the figures that I absolutely
did want to purchase and were more than not already sold out.
My goal for 2014 is to analyze each purchase before I pre-order, and gauge both the manufacturer as well as the sculptor. I'll carefully per-use all available pictures, and try to decide whether it's something I absolutely want in my collection. For instance, I have Irma [Queen's Blade] coming in my July 2013 AmiAmi order and I could have done without her. I'm sure she'll be a fine figure, but it's not one that I
need [in retrospect]. Lucifer and Elf that are bundled with her, though? Those I desperately require.
It seems to be a habit of me to pre-order as soon as the item hits AmiAmi since I'm afraid it will sell out immediately due to popularity, but that rarely happens. Even ones that are immensely popular, such as Tharja, are still available months later. I need to train my finger not to react on impulse and think things through before-hand.