Make a realistic assessment of how tangled your personal finances are - do NOT underestimate the mess you are in.
Keep track of each cent spent/received - it is important as small transactions could introduce a wide gap between your expectations and the reality.
Plan ahead - make sure that you plan well ahead and budget in advance for bills, rent, food, clothing, shopping and other expenses.
Use a reminder/calendar, if necessary.
Monitor your finances regularly.

And, most importantly pick up a personal finance software that is not a chore to learn but a pleasure to operate while at the same time does most of your work for you. While choosing a personal finance software, you must ensure:
Ease of use: It should not take you more than three logins to master the software. The simpler it is to use, the more encouraged you will be to use it regularly.
Category-wise Finance documentation : A good money management software should let you classify your expenses under customized headers like commuting, health care products, car repairs and other uncommon categories. In addition, pay attention to the number of such fields you are allowed to create. The more, the merrier. All finance management software will offer you the standard fields of filing expenses under Bank loans, Bank Credits, Bills, Shopping etc but that cannot always cover your needs explicitly.
Account Accessibility and Security : The smarter option is to go for a web-based finance management software. Compared to the ones you need to download and install, web based interfaces enable password protected account accessibility from any corner of the world. Simply log in via an Internet connection and update your finances on the go. It's great for those who are frequently on the move, while ensuring that their online records are safe and secure.
Moreover, improved features are frequently added to such software. A web based finance management software lets you enjoy these updates (often) free of cost, unlike the desktop based versions that you have to download afresh.
Reminders and Alerts: An intelligent software will allow you to set email reminders for paying bills, filing tax returns etc, insurance premiums and other important issues.
Budget: Budgeting in advance is critical and your personal finance software must allow you to set aside budgets.
Report generation and Printing: A powerful report generation mechanism is essential for continuous monitoring of your finances and planning accordingly.
Multi-currency Support: A finance management software is of no use to you if doesn't support the currency you use! Choose accordingly.

Keep the above points in mind while making your choice. Make a commitment and use all the features of the finance management software well. You will certainly see a significant improvement in your finances.