you get that impression don't you?
I think it all depends what sector you're aiming at. Are you a web designer/developer? Are you a graphic designer? Do you do print & web? Can you illustrate? Can you take photographs? --- Even if you are technically aiming at one area, you can cross diversity if they links add value to your business. An example might be illustration if you're a designer (a common one) or a typographer (less common). With web that might be
SEO (many many, though less common those who can practice what they preach) or perhaps you can add flash (quite common, but often used badly). But don't try and be everything, because you'll stretch to thin - better to be great at 1 or 2 things than average at many things.
Once you've worked out where you're interests/skills lie, you can begin to target. I'd go on toon's advice of starting from an job, since this gives you a nice cushion from which to start. You don't need the business to make money since you're only doing it on the side, so you can get though that lag time where jobs are few and lower paid, until they are more numerous and you can charge more.
Now your USP? you can either make it something that is based on
1> Price
2 >Doing it a bit different
3>Being new
Effectively, you can't do all of these. If you try, you may end up with a expensive product no-one gets or a massively undervalued product thats selling like hot cakes, but you've got it sooooo cheap you'll making nothing on it. They work out like this:
1> Price - I'll undercut my competition by creating great graphics for less
2 >Doing it a bit different - I've got a certain style thats quite fresh, and it's a great way to do x or y
3>Being new - I've invented a new way of marketing that's bound to reach everyone who wants to use it. I'll print on urinal cake!!! (it's been done, sorry!)
Mostly, print studios tend to use a mixture of 1 & 2, studios/agencies tend to use 2 & 3 and freelancers use 1,2 (or 3 if they are lucky). It must be noted though that 3 is hard, but if you have the ideas... agencies can be powerhouses for these sorts of things, and have the clients, or more to the point, budgets to pull off the clever new idea.
Man, I've rambled on... I'll stop here.