These are more focused on just getting into what we perceive as good habits, and its always best to egt into good habits from early on! Some of these are somewhat obvious, maybe even dumb but its easy to forget the simple things. Hope they help.

1) Ensure that your client is pleased with what you have produced. Testimonials and thorough feedback is key to this. It gives the client the opportunity to feedback on your work and also how you were to work with. This will help you resolve any dips in your own performance that may not necessarily be in your work but in your business mentality for instance.
2) Do not copy, be overtly influenced, re-create another designer’s style. Forge your own looks, techniques and approaches. It is the only real, lasting interest in your work. Be original. You must discover and find out what your own USP is.
3) Where possible, make sure you are given credit for the work you have done. i.e, if you have designed a website, ask to have your link in the footer or on the credit page. This will lead to more traffic and interest from others who want work in a similar vein.
4) Deadlines. At all times produce work to the agreed deadline; unless you have agreed an extension. If you realise the deadline will be missed or is not possible, ask for more time before you take the job; or as soon as you realise into the job that the deadline is unworkable. If you spot problems, resolve them early on is the lesson.
5) Print work. When you design for print, try and chase up copies of the finished product. Your client, should be happy to let you have two or three copies free of charge. These make for a more complete portfolio.
Anyone have any other random tips?
Reference:
Creative Image Making (Zeegen, Lawrence 2005)