I have developed these based on my freelancing experience. Though I have discontinued freelancing, but would like to share my practices with you. These are basic practices and have been developed over time with experience (good and bad). Please feel free to leave your experiences and comment on this article.
1. Communicate with your clients frequently
This I believe is the most important habit that you should inculcate. Keeping the client in the loop ensures them that you are on top of things and that you are working on their project. Think about it! what if you were the client and were paying someone to develop something. Wouldn't you want to hear from your vendor frequently? Issues, slippages, project statuses should be frequently updated to the client (irrespective if your client asks or not). It’s professional ethics!
2. Document interactions with your client
Following point 1, you will have a lot of interactions with your client. You should record/document these interactions as a habit. These interactions could either be in the form of a chat message, emails or function specification documents. Maintaining a history of such interactions will help you during the closure of the project and mainly towards User Acceptance Testing (UAT).
3. Maintain on-going relations with all parties
Just because a project is over does not mean that you should not maintain relations with your clients. Greeting your client on birthdays, anniversaries, etc makes them feel good. This exercise is good to build rapport with clients. It always keeps you fresh in their minds. So, the next time they have a project; guess who gets called first. In addition to above, you should also maintain relations with suppliers or other freelancers who you outsource work to. In the long run it helps build trust and gives you a good bargaining power. Think about it.
4. Get yourself a professional identity
So what if you freelance, it doesn't mean that you should not carry yourself professionally. Create professional looking logos, business cards, stationery and website (very important). Get a professional copy writer to help you with the content of your website. You should mention the projects that you have done and the skills that you have. Always have a contact form on your website where prospective clients can contact you (and when you do get contacted, reply immediately).
5. Seek testimonials from your clients
Seek testimonials from your clients after closing a project. Get this on email and catalogue it for future reference. Also seek their permission to publish their testimonials on your website. In addition to this, you should consider requesting permission from your clients if its ok to give their contact information for reference checks. Some prospective clients would like to talk to your old clients and gauge the experience they have had with you.
6. Create reusable libraries
Creating reusable libraries makes you more profitable. Think about it! If you have been creating email validators on forms for nearly all projects, it makes more sense to create a reusable library and import that library in your current project and make use of it. This way your effort on the project in the long run is reduced and hence you get paid for something that has already been done. In addition to this, if you discover a bug and fix it, you can apply a patch immediately to all your projects. Saves your time there too and helps all your clients with the bug fix in one go.
7. Maintain proper accounts
Many freelancers (including me) have failed at this. We fail at this not because we don't know how to handle finances or accounts, but because we are programmers... we love to write code... not books. Do you agree with me?. But the hard reality is that at the end of the financial year we need to pay taxes. To pay taxes properly we need a good accounting system. The choice is up to you, either be disciplined and maintain proper accounts from day one or waste a lot of time towards the end of the financial year doing it. I recommend that you do it as you go along. I recommend that you dedicate a weekend to file your papers/accounts properly. Please feel free to post your comments or add to this list your experiences and best practices.