Replying to [yufang]:
The market for products in all countries are not the same, and you need to look at each one to verify how that product is selling in one country, as for new products you would know if that will do well or not depends on the market type and sales of products in that area before, like most electronic goods sell well in UK but if you sell in parts of China, the same products would not sell, if people have a need for a product they may buy, not easy to sell them a item they don't want or can not use, or they can not get the money to buy it.
In UK i i want to buy a car, most people would lend money from the bank or where they would buy the car from, if they could not get the money, so means no sale, we always need to look at the people that buy these goods.
Samples are always a problem to give, if the sample is cheap then your choice is to give or not, but you job is to check the buyer too and make sure they may make an order in the future ?
If the buyer is from UK and they are called " Bargain PC's"
and they want to buy monitors for the PC's from you !, and want 1000pcs, being a LTD company and they have a website too, also have correct email, and maybe they have bought before from China, maybe they have been to China to vist suppliers or will come later, they contact details, what about their know how for the goods?
Where they sell their products in UK?
I would have no problem to send a free sample if i thought the buyer is good and that they could have a chance to deal with me as a supplier for them, this is a open door for me, but i would make sure that this information was real, or maybe just try get you product cost back from them, and work the cost with the shipping.
At the Canton fair we spoke to many people that wanted an extra 30% more for the sample cost, as i am there to buy for our company i do know we would choose another supplier if they were lower, and yes sure we check the quality and production at all times, but the price in the product is at the front on most items.
Hope this helps,