Hi again :)
The best idea is to have a flip through magazines, newspapers etc and keep your eye open for trends and potential niche markets that you can capitalize on. You can buy things like fashion jewelry, craft materials, toys and so forth very cheaply from Asia and resell it for a tidy profit. For example, recent trends have been for scrapbooking, knitting etc. Then there are some great home decor items - take a look in stores like Freedom etc and then try and find a supplier in Asia who sells something similar for cheaper. That's just an example, you could do the same thing in lots of other areas.
Whatever ideas you have, I suggest using the research and analysis tool to find out the demand on eBay sites and general internet searches. It's a great way to get a feel for whether your idea is worth pursuing.