1. Items under $10
It sounds like a great idea - after all, everyone likes a bargain don't they? But items that sell for under $10 have one big problem: Shipping. It's quite likely that the shipping for the item will cost more than the item itself and this can be very off-putting to buyers. For example, if the item costs $4.50 and shipping costs $6, the total cost for the item is $10.50.
If the buyer can purchase the item at their local store for $8, then this suddenly becomes a much better deal. For small items and accessories, the way to get around this problem is by grouping the items together, such as sets of 6 golf-balls or 5 tea towels.
2. Products everyone else are selling
Many sellers think that the best way to get started on eBay is to sell items that everyone else is selling. Surely those super hot items such as ipods, cell phones, psps and so on will be a quick route to riches? Well, no. The sellers who are already selling these items are not only more established on eBay - and thus familiar to and trusted by buyers - but they will be able to buy wholesale stock in larger bulks lots than you will, so their prices will always be better. Thus it will almost certainly be very difficult for you to make a profit in a market that is already well supplied.
3. Things you love...but no-one else does
Hobbies can be a great way of making money, but only if plenty of other people are interested in them too.
Another scenario is when you find a product that you think is absolutely wonderful and could be the next best thing...but no-one seems interested in buying it. Oh well you think, it's only short term, eventually they'll learn about my item and start flocking to buy it. Ah, no they won't.
It's lonely work trying to educate people on the benefits of a product all on your own. As fabulous as the product might be, it's nigh-on impossible to start a trend on your own.
To make money from a trend, you need magazines and newspapers, word of mouth and television to do some of the work for you.
4. Difficult items to ship - e.g. fragile china and plants
Now I'm not saying that these are bad items to sell altogether. Many sellers do very well from these items. But I don't suggest you sell such difficult items when you are first starting out. Both these items have an above-average shipping risk, particularly if not packed properly. As a new seller, any negative feedback you receive at this early stage could be especially damaging to your career.
5. Very large items
Thinking of starting with furniture or pianos? Unless you already have experience selling and shipping these items, then it might be wise to start with something smaller. Shipping such large items is a major operation. Not only that, these items will sell less often than mid-priced items as they won't attract the same number of impulse buyers.