Some of the things I consider in decisions are of course trade-offs and real long terms pros & cons of various options. You have to weight by how often you use things and how much of a delta there is from the other choices per use. Then you consider opportunity cost - the value of other things you could do if you make alternative decisions. You have to also consider your various life plans for your future and how your decision is rated in those different scenarios, and then weight them by their probability. You have to consider the transaction cost and how hard is to get out of if you are wrong.
Then you also have to be aware of your own emotions and prejudices; you are after all human, you can't remove irrational thoughts, but you can try to identify them and compensate for them; but be careful not to over-compensate (eg. don't exclude Bill Hayden from your search for the mole just because he's sleeping with your wife).
Obviously you aren't just rating the cold numerical factors; some things may be bad bargains but give you a good feeling; that should be assigned some value. You have to consider the probability of problems (such as ebay scams or car mechanical troubles) and give them a cost rating and weight by their probability (and obviously the cost should involving a valuation for your frustration factor and mental anguish and time cost).
Most of all, you also need to evaluate the time cost of the decision making process itself; for example people who value-hunt for cans of greenbeans are retarded, just buy the one in front of you, but with larger things it's more graded and complex.
Finally and perhaps most complex at all, you must also apply these decision processes to the meta-decision of deciding what goes in your decision criteria. You have to consider each of the decision factors and decide if the time spent considering it is worth the benefit to the quality of your decision, and then either exclude or include or approximate it.
Speaking of Jimmy Carter and George Bush - it's sort of funny to me how much people admire quick decision makers like The Decider. We don't really care that much if people around us make good decisions, we just want them to fucking pick and hurry up. This goes from the most trivial situation to the most important.
For example, if you're going out to lunch with coworkers and you say "where should we go?" and they're all like "ehh, I dunno, maybe that indian place? or thai, I'm not sure", you think "urg, you're annoying, I won't ask you again".
One thing I've learned about dating is that almost all girls want you to make all the decisions, even the independent strong liberated ones. Of course they want to have veto power and boss you around at will, but when it comes to the mundane daily decisions - where do we go to eat, what should we do tonight, etc. - you better have a decision and you better make it quick, or you are a wishy-washy loser in her eyes. A guy who can take the lead and command a situation is very attractive. Hell, I know it's wonderful to just be able to relax and have someone else lead you around and make all the decisions unless you choose to step in. It doesn't actually matter if the decisions are great, just make them without a bunch of wishy-washing or caveats (though there may be short term complaining about your bad decisions, that should be ignored).
(We also really admire people who are foolishly impulsive & do really stupid harmful things for fun whims or romance. And we love people who are "passionate" aka violent or have big tempers and scream and all that. But those are other rants.)
Sometimes you have to make the meta-decision to simply not even consider a whole class of choices. For example when I was young I used to consider the cost/benefit of food when ordering at restaurants. Most people who even consider price do it all wrong, they just see "that's too expensive" ; instead you should be looking for value, something expensive is worth it if it's special, if it leads to having a nice date, if it teaches you something about food. Anyway, doing that consideration all the time is just exhausting and not worth it once you have any money, so I decided not to make that decision any more.
Another case is when you know that you have irrational biases that are too strong and you simply cannot trust yourself to make a good decision. In that case you have to simply make rules for yourself to eliminate the decision point. Alcoholics of course know this, rather than being reasonable and letting themselves have a little drink once in a while and decide when to stop, they know they can't make that decision and just make the draconian rule to never touch the stuff. But there are lots of cases of this.
For example I know that when my future is uncertain, I am almost always too cautious; that is, I fail to commit to things when I think it's likely they may not last. e.g. I've never bought a house because I feel like I might move at any time. And I tend to never decorate or buy furniture or curtains or whatever because I feel like I might move out of the current rental at any moment, so why invest in making it nice? What I know now is that it's almost always better to just pretend that you are in fact staying in your current place forever and make the investment to make it nice and get all settled in. Worst case you have to move and then you do it all over again. That's not really that bad, the alternative of constantly living like you're about to move out is much worse.