We use debit cards.In fact, we haven't had a credit card for several years. The last one was AmEx that we cancelled after a vacation in Mexico in 2004.
The real disclipline is "acting your wage", and getting rid of your debt. Imagine how much money you would have to invest each month if you didn't have car payments, credit card payments, student loan payments, etc.
In the last six months we have paid off a car loan, my student loan, and back taxes I owed from a failed business venture. Next up is another car loan and my wife's student loans. Every time we pay something off, it's like having that much more income every month.
The only problem we've had NOT having a credit card was in 2002 when we when to Florida and were unable to rent a car (that's why we got the AmEx card). Still, we decided it's better to take a cab than pay and pay and pay credit card bills!
Apologies for hijacking the thread...