Do everything with design in mind. That design should be to communicate in the easiest and most concise manner to your audience, to make it as easy for them to understand, talk and buy from you. To get them to do the one thing that is most important, be that to sign up, or buy, or give you permission to contact them.

I was at an internet marketing seminar today which was jam packed full of general information I already knew :p We had the opportunity to hear from a very successful Australian marketer. The information provided was great, but I had heard it all before.

What really stuck for me though,  was making the process as simple as possible for your clients and customers. 
Don't make them jump through hoops to register with you or buy from you. If they're on your site, or reading your email or ad, then they have an interest in what you have to offer. So make it easy, idiot proof, so simple that a kid could process the order.

If you're going to set up a website, decide in advance exactly what it's purpose should be. Each and every page should have a purpose, a design, an intended goal...

and I'll tell you that for free