Customers are your most precious resource. It takes a long time to build up a portfolio of good customers that you have a long-lasting relationship with.
Ideally your customers know what they want, are able and willing to pay for it and value your contribution.
In practice though, it is not always that clear cut. Plenty of customers do not know exactly what they want, but hopefully they have a good idea, and together you can fill in the blanks.
What is important here is that no matter what kind of consultancy you do, there are patterns that are common to all forms: A customer will approach you because they either heard from someone that you are good at what you do, or they have read about you somewhere or found you on the net. At this point an interviewing ritual starts, the prospective customer will want to get the idea that they are in good hands, you want to make sure the customer is of good standing and knows what they want.
- During this phase you meet, usually once or twice, to flesh out the details of what needs doing. If possible, go to their premises at least once and look things over. If it looks like you wouldn't want to work there if you were an employee then it is probably better to let it go. Yes, you read that right, not all customers are customers that you want to have, and one part of this is whether or not you would want to work for them in a regular job. The point is that if you wouldn't want to be a regular employee you *really* don't want to be a freelancer working for them. As a rule the expectation is that a freelancer works harder, brings to the table more expertise than a regular employee (otherwise why hire an outsider) and deals with higher level management more frequently. The difference is in the level of pay and their ability to quit hiring you and your ability to stop working for them after completion of a job.
- Customers should be able and willing to pay for your services. This seems like it goes without saying, but unfortunately, not all customers are able to pay for your services, and even if they are not all of them are willing. It is up to you to make sure that they are. One way of making sure that the whole estimate-work-invoice-payment cycle runs smooth is to build in a little threshold right at the beginning. 10% down on taking on a job is a fairly reasonable amount if you have a good reputation and lots of places where you could be working. If you are just starting out you could change that in to weekly invoices, with a 7 day payment term. That way you are out at worst 2 weeks of work if a customer is not of the 'able and willing to pay' variety. And if after that period you do not get paid, seriously, walk away! There is nothing worse than a customer that does not pay when invoiced. It's better to have 20 small customers that pay small bills on time than it is to have one big one that pays large bills too late or never. That can seriously mess up your continuity and in an extreme case could cause you to go under.
Remember: Happy customers are repeat customers, and repeat customers are a lot more profitable than one offs. So if you have to go through all the overhead of a new customer for every job you will never make money enough to save. Better to have a group of reliable repetitive customers and occasionally add one or remove one than to have a wildly varying set of contacts every month.