Here are a few ideas to start with:
Remember all along that God wants his right place in your heart. Don't get lost in tactics alone, forgetting that God desires you to be financially free to serve him first. Pray for encouragement, discipline, and accountability in your journey.
The best place to start changing your spending habits is to know what you're spending money on. Track and categorize your spending; it doesn't have to be complicated. You can use Microsoft Money, Quicken, Excel, or a pad of paper and a #2 pencil. Start simple and don't over-categorize.
Develop a budget. Again, start simple. The purpose of the budget is to decide where your money will go before you spend it. Put your tithe on the top line of expenses.
Get out of consumer debt. If you have credit card balances, pick a strategy and pay them off. Cut them up if they are a problem for you to manage. Take care of student loans, cars and other debt. Most people are comfortable with a house loan; but pursue wisdom in borrowing. Don't put yourself in a situation where you're enslaved to your mortgage. Own you're house, don't let it own you.
Cut some stuff. Sell things or discontinue unnecessary purchases that push you further into debt each month.
Try going "cash-only" for a few months. Take your budgeted amount for the month out in cash, and put it in envelopes for each category. This is a great way to develop discipline.
Find accountability. Walking through these changes with someone else who seeks to honor God with their finances is most often the difference between success and failure.