rule #1 -- never buy something that you can't pay-off immediately if you needed to. siyempre exception to this rule would be bahay, kotse, etc.
don't develop the mentality that most americans have -- they only think about the minimum monthly payments or what their monthly budget will be. they don't think about what they'll end up paying over time. and by only paying the minimum, nababaon at nababaon lang sila sa utang.
however, there are smart users of credit cards. daming credit card companies will offer 0% financing promos for X months. if you are sure to pay your balance by the end of that period, sige, avail of the free use of money. but don't forget rule #1.