The most basic of advice...

They say you only have once chance to make a first impression.  That is true, but I find that in this business I there are at least three first impressions.  At some point a potential client is going to have to learn of you.  This could be through a referral, your web site, advertisement, etc.  I don't expect anyone to call for an appointment if the work you have done for their friend is poor, if your website is unnavigable, or the phone number is incorrectly listed in your ad.

The second "first" impression is going to be your initial phone conversation.  I cannot stress how important it is to call quickly and to during a reasonable time.  I suggest you call every client within 24 hours of getting their information.  Call no earlier than 10:00am, and call no later than 7:00 (even that may be stretching it).  Don't call on Sunday or on major holidays, and if you get an answering machine LEAVE A MESSAGE.  Document the date and time of your calls.  If you leave a message and don't hear back call again in a day or two.  Sometimes people lose your number or can't understand the recording.  If you don't hear back from the second call wait a week (they could be on vacation).  If after three messages they don't call you back then don't keep calling.  If they are interested they will get back to you.  I have had people cal back 6 months or a year later stating that now they are ready to begin.

The third "first" impression is when you arrive in person.  Nothing tells a customer that you don't value and respect their time like showing up late (except maybe not returning phone calls).  While some parts of the country believe that 5 minutes early is 10 minutes late others expect you to arrive exactly on time and not surprise them before they are ready.  In general the earlier the appointment the less acceptable it is to show up early.  That being said leave your home or office early.  Arrive early.  You can always wait around the block, but if traffic is bad (as it always is in the DC metro area) that time might be needed.

So, in review.  Call in a timely fashion, leave messages, arrive on time.  If you also return calls in the same manner you will have a big lead on your competition, far too few people do the above.

If I forget remind me some time, I think a discussion of artistic vs. professional appearance is another good topic.