What is the best way to approach prospective clients?
What is the best step to approach prospective clients, other than advertising online or sending out brochures?
Referrals from existing clients is a good opportunity. Make sure you regularly ask your cuirrent clients if there's anyone they could refer you to.. maybe even offer referal bonuses ?
It is a big question. One thing you may like to consider is that successful marketing never takes on a single pronged approach. The more irons you have across different medias/ mediums the better. Just make sure you keep measuring, measuring, measuring. I can not stress this enough. If you don't know the return you are getting for your marketing spend then you are really just burning money.
If the intent of your question was to find some inexpensive ways to generate new leads then Andrew has hit the nail on the head. Your existing clients are always a great source for new clients as they already know, like and trust you.
You can also try networking - both online and offline. Join groups that your target clients are in. Go to local events - basically wherever your clients are likely to go. It takes time and effort but it does work.
The first step is to narrow down who your prospective clients are. And "small business" doesn't cut it ;)
For example, in my software business, I'm interested in small service businesses that have between 2 and 10 staff and more than $2 mil in annual revenue, or professional consultants who generate in excess of $300k/year but have no staff.
In order to target these people I have setup a new brand called The Procedure People http://www.theprocedurepeople.com/ -- my goal is to identify business owners who have solved their sales problem but are having trouble growing due to lack of infrastructure. When I did some keyword research in Google AdWords, I found people looking for help with "policies & procedures", my hypothesis is that those people are exactly the target market I'm after (or at least a portion of them are).
But without first stating very clearly who my ideal client is, I wouldn't have been able to come up with a creative way to get access to them.
You're running a PA service: who is your ideal customer? Do you want to access solopreneurs (eg. on Flying Solo) or do you want to access professional consultants? What about picking an industry? Can you be particularly helpful to anaesthetists? Accountants? Lawyers? GPs?
Anyway, you get the point: the answer to the question "how should I get in touch with my prospective clients" will depend on who those prospective clients are. Identifying who they are is often more challenging, than trying to find them ;)