It's human nature NOT to want to miss out. I have a friend that uses a perfect phrase to sum this up: FOMO (fear of missing out).
You can tap into this "fear" when marketing, by creating scarcity. Whether it's a limited number of items, or a strictly limited time, you create a sense of urgency with those you're marketing too. It's perfect for marketing events (only 17 seats left!) but it can be used much more broadly also.
I subscribe to updates from a fashion site, Igigi. They've taken this to heart and they run semi-regular 6 hour sales. How do I know this works for them? Because they keep doing it! As a test case of 1, I would click to see what's on sale at least 50% of the time, despite the fact I've yet to ever buy from them.
Virgin Blue have a similar tool, although it's even shorter and more regular. They have "happy hour" bookings from 12-1pm on a weekday.
So the zero budget marketing tip for today is to consider - what can you create scarcity around to drive short term sales results?
ps. Just come across another great time limited promotion on a craft education blog, Blacksburg Belle. I had an email prompting it at 1.30am (as it's a US site) and when I clicked on to learn more at 7am, the "10 places only" offer was filled. So more evidence of time limited/space limited offers being effective.