Hi toys4cheapstore, thats a really nice question,
This is something which generally is a tough nut
to crack for new online marketers.

By the way I don't know about you and your
experience as an online marketer, I am not a
guru, but wharever practical knowledge I have
I won't mind sharing with you.

I am giving you some tips, more than that it's
not possible or else I might have to write an
e-book. Here are the tips:

If you are a newbie plese don't create a
a product of your own, atleast for the time
being, better join an affiliate program and
promote it, don't join more than 3 program,
do it for atleast 3 months and alongside
learn the tricks of online marketing.

If you are a bit experienced and if you have
a hobby or if you are passionate about any
particular subject, search for it on your favourite
search engine.

Suppose you like photography search the keyword
in google,yahoo,msn etc . Just by looking at the
result you can know weither there is a market or
not. There are also lot of keyword tools which will
help you know how many searches are done on
a perticular keyword in a perticular month or day.

Before you start creating your product remember it's
best not to bang your head where there is lot of
compitition. It's better if you opt in for a Nice Market.

Suppose your subjet is photography please don't
make a site and a product on the keyword"photography"
narrow down your search, you can use the keyword as
"star in action photographs", "animal in nature
photographs" etc.

Though the number of searches will go down yet you will
get visitors who are intrested in your subject only, your
visitors to customers conversion ratio will also be high.
though.

Once you found the right keyword create your product,
it can be an e-book, e-report, service anything. Well if
doing that is beyond your capacity hire someone, it's
easily avialiable online . One good site for this is elance.

One more tip, fourms are great place to find products
be a member of the fourm which relate to your subject.
You will get to know what the people in general need.

Hope this tips might be of some help to you. If you want
more just pm me, I will be willing to help you.

To your success
Amitabh