I imagine a lot of people on this forum are already tracking their spending, probably using a spreadsheet. I started off recording mine on a spreadsheet too but found it a bit cumbersome. So I wrote a simple online app which I've been using for 18 months now:
Simply record transactions - a date, an amount, whether it is an income or an outgoing, add some tags (just like threads on this forum), you can also add longer notes (useful for order/reference numbers etc.) & that's all you need to do.
The tagging process is a really easy way of organising your costs. I was quite alarmed when I found out the true cost of my car!
Please feel free to give it a go, it might be useful to you too.
Any other bits of software that people use?