The first time I got this question, I was completely stuck. My stuttering answer was: "someone who pays me on time".
It took me awhile to arrive at understanding my ideal customer, mainly because I kept trying to think of it in terms of industry or type of app (I'm a programmer). Eventually I figured out that for me these attributes were irrelevant. Instead I tried to broaden my thinking in terms of client attributes. Consider these basic attributes that will apply to most clients:
- Size (small or large)
- Location (local or non-local)
- Age (established or start-up)
- Speed of change (nimble or methodical)
- For profit / non profit / gov't
Think about the people you will work with inside the organization as well, and their attributes:
- Age (young or older)
- Communication style (electronic / voice / in person)
- Detailed or high level thinking
Depending on what you do, you may also consider your ideal project with attributes like:
- Team size (small or large)
- Role on team
- Process structure
- Communication structure
You may not have opinions on all these things, but try to pick one extreme or the other as much as possible. As you said, you want to identify your ideal client to develop more effective marketing, but you will often end up with clients that are close to your ideal client but not exactly meeting the criteria.
Also, let bad experiences guide you. If you had a bad experience with a client once, think about their attributes and consider choosing an opposite attribute for your ideal client.
Depending on your business, there will likely be other attributes that are relevant to you. For me, type of technology, and the tools that will be used are relevant.
Here is an example of my current ideal client (excluding technical stuff):
- Local small business (< 50 employees)
- My contact is the owner - so he can make the money decisions
- He is tech savvy - may have been a programmer previously but now focuses mainly on the business
- For profit, not non-profit or gov't
- Company has been around at least 10 years
- Most communication via email or phone
- Detailed person
- Decisive - doesn't change his mind repeatedly
- Sees me as a partner, not a vendor
For me, this really helped because I now have a clear picture in my head of the kind of businesses and people I want to work with, and I can tell fairly quickly if a project isn't right for me because they will miss on multiple criteria.