I advocate the 80/20 rule, and apply it to most things. What the 80/20 rule generally is, is you live on 80% of your NET, and net is important here because we never see our gross. The remaining 20% of our net we put into a savings account, high interest bearing account such as a CD, money-market or mutual fund. Or we invest it in the stock market (having done your homework well on the latter of course before diving in). You then apply that 80/20 to every big ticket item you purchase.
If you can afford a $25,000 car, start looking for one that will only cost $20,000. If you can afford a $200,000 house, start looking for homes for $160,000.
One very important thing to keep in mind is that saving is not about sacrificing. It's about living within your means today so that tomorrow offers more financial security and choices. People who 'live for today' and spend like they are going to die tomorrow are actually ultimately sacrificing more than those who put aside money for a rainy day. They typically work more hours to pay for stuff, and they work many more years because they can't afford to retire.